Medical treatment system and methods using a plurality of fluid lines

ABSTRACT

Improvements in fluid volume measurement systems are disclosed for a pneumatically actuated diaphragm pump in general, and a peritoneal dialysis cycler using a pump cassette in particular. Pump fluid volume measurements are based on pressure measurements in a pump control chamber and a reference chamber in a two-chamber model, with different sections of an apparatus being modeled using a combination of adiabatic, isothermal and polytropic processes. Real time or instantaneous fluid flow measurements in a pump chamber of the diaphragm pump are also disclosed, in this case using a one-chamber ideal gas model and using a high speed processor to obtain and process pump control chamber pressures during fluid flow into or out of the pump chamber.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.14/732,571 filed Jun. 5, 2015, now U.S. Pat. No. 10,058,694, whichclaims the benefit of the following:

-   -   U.S. Provisional Application No. 62/008,342 filed Jun. 5, 2014;    -   U.S. Provisional Application No. 62/155,937 filed May 1, 2015;        and    -   U.S. Provisional Application No. 62/159,737 filed May 11, 2015.

The above applications are hereby incorporated by reference in theirentirety.

BACKGROUND

Peritoneal Dialysis (PD) involves the periodic infusion of sterileaqueous solution (called peritoneal dialysis solution, or dialysate)into the peritoneal cavity of a patient. Diffusion and osmosis exchangestake place between the solution and the bloodstream across the naturalbody membranes. These exchanges transfer waste products to the dialysatethat the kidneys normally excrete. The waste products typically consistof solutes like sodium and chloride ions, and other compounds normallyexcreted through the kidneys like urea, creatinine, and water. Thediffusion of water across the peritoneal membrane during dialysis iscalled ultrafiltration.

Conventional peritoneal dialysis solutions include dextrose inconcentrations sufficient to generate the necessary osmotic pressure toremove water from the patient through ultrafiltration.

Continuous Ambulatory Peritoneal Dialysis (CAPD) is a popular form ofPD. A patient performs CAPD manually about four times a day. During adrain/fill procedure for CAPD, the patient initially drains spentperitoneal dialysis solution from his/her peritoneal cavity, and theninfuses fresh peritoneal dialysis solution into his/her peritonealcavity. This drain and fill procedure usually takes about 1 hour.

Automated Peritoneal Dialysis (APD) is another popular form of PD. APDuses a machine, called a cycler, to automatically infuse, dwell, anddrain peritoneal dialysis solution to and from the patient's peritonealcavity. APD is particularly attractive to a PD patient, because it canbe performed at night while the patient is asleep. This frees thepatient from the day-to-day demands of CAPD during his/her waking andworking hours.

The APD sequence typically lasts for several hours. It often begins withan initial drain phase to empty the peritoneal cavity of spentdialysate. The APD sequence then proceeds through a succession of fill,dwell, and drain phases that follow one after the other. Eachfill/dwell/drain sequence is called a cycle.

During the fill phase, the cycler transfers a predetermined volume offresh, warmed dialysate into the peritoneal cavity of the patient. Thedialysate remains (or “dwells”) within the peritoneal cavity for aperiod of time. This is called the dwell phase. During the drain phase,the cycler removes the spent dialysate from the peritoneal cavity.

The number of fill/dwell/drain cycles that are required during a givenAPD session depends upon the total volume of dialysate prescribed forthe patient's APD regimen, and is either entered as part of thetreatment prescription or calculated by the cycler.

APD can be and is practiced in different ways.

Continuous Cycling Peritoneal Dialysis (CCPD) is one commonly used APDmodality. During each fill/dwell/drain phase of CCPD, the cycler infusesa prescribed volume of dialysate. After a prescribed dwell period, thecycler completely drains this liquid volume from the patient, leavingthe peritoneal cavity empty, or “dry.” Typically, CCPD employs 4-8fill/dwell/drain cycles to achieve a prescribed therapy volume.

After the last prescribed fill/dwell/drain cycle in CCPD, the cyclerinfuses a final fill volume. The final fill volume dwells in the patientfor an extended period of time. It is drained either at the onset of thenext CCPD session in the evening, or during a mid-day exchange. Thefinal fill volume can contain a different concentration of dextrose thanthe fill volume of the successive CCPD fill/dwell/drain fill cycles thecycler provides.

Intermittent Peritoneal Dialysis (IPD) is another APD modality. IPD istypically used in acute situations, when a patient suddenly entersdialysis therapy. IPD can also be used when a patient requires PD, butcannot undertake the responsibilities of CAPD or otherwise do it athome.

Like CCPD, IPD involves a series of fill/dwell/drain cycles. UnlikeCCPD, IPD does not include a final fill phase. In IPD, the patient'speritoneal cavity is left free of dialysate (or “dry”) in between APDtherapy sessions.

Tidal Peritoneal Dialysis (TPD) is another APD modality. Like CCPD, TPDincludes a series of fill/dwell/drain cycles. Unlike CCPD, TPD does notcompletely drain dialysate from the peritoneal cavity during each drainphase. Instead, TPD establishes a base volume during the first fillphase and drains only a portion of this volume during the first drainphase. Subsequent fill/dwell/drain cycles infuse and then drain areplacement volume on top of the base volume. The last drain phaseremoves all dialysate from the peritoneal cavity.

There is a variation of TPD that includes cycles during which thepatient is completely drained and infused with a new full base volume ofdialysis.

TPD can include a final fill cycle, like CCPD. Alternatively, TPD canavoid the final fill cycle, like IPD.

APD offers flexibility and quality of life enhancements to a personrequiring dialysis. APD can free the patient from the fatigue andinconvenience that the day to day practice of CAPD represents to someindividuals. APD can give back to the patient his or her waking andworking hours free of the need to conduct dialysis exchanges.

Still, the complexity and size of past machines and associateddisposables for various APD modalities have dampened widespread patientacceptance of APD as an alternative to manual peritoneal dialysismethods.

SUMMARY OF INVENTION

In one aspect, a system is disclosed for measuring an amount of liquidin a pumping chamber of a pneumatically actuated diaphragm pump. Thesystem comprises a fluid inlet and fluid outlet valve connected to thepumping chamber; a diaphragm separating a pneumatically actuated controlchamber from the pumping chamber, the control chamber fluidly connectedto a reference chamber of known volume via a conduit that includes areference chamber valve; the control chamber fluidly connected via oneor more actuation valves to a source of positive or negative pneumaticpressure; and a controller configured to control the fluid inlet andoutlet valves, the reference chamber valve, and the one or moreactuation valves, and to receive pressure data from a first pressuresensor connected to the actuation chamber and a second pressure sensorconnected to the reference chamber. The controller is configured toisolate the pumping chamber by closing the fluid inlet and outletvalves, charge the control chamber with a first pneumatic pressure; ventthe reference chamber or fix a pneumatic pressure in the referencechamber that is different from the control chamber pneumatic pressure;measure a first control chamber pressure and a first reference chamberpressure, connect the control chamber to the reference chamber byopening the reference chamber valve, measure a third equalized pneumaticpressure in the control and reference chambers, and compute a controlchamber volume based on an ideal gas model that assumes an adiabaticpressure equalization process in the reference chamber and a polytropicpressure equalization process in the control chamber.

The model optionally can further assume an isothermal process in theconduit as a gas moves from the control chamber to the reference chamberduring the equalization process. The model applied to the controlchamber can also use a polytropic coefficient in the ideal gas model,wherein the controller is programmed to vary the polytropic coefficientas a pre-defined function of the control chamber volume. The controllercan also be programmed to compute a polytropic coefficient based on anestimated volume of the control chamber using a model that assumes anadiabatic pressure equalization process in the control chamber.

In another aspect, a system is disclosed for measuring an amount ofliquid in a pumping chamber of a pneumatically actuated diaphragm pump.The system comprises a fluid inlet and fluid outlet valve connected tothe pumping chamber; a diaphragm separating a pneumatically actuatedcontrol chamber from the pumping chamber, the control chamber fluidlyconnected to a reference chamber of known volume via a conduit thatincludes a reference chamber valve; the control chamber fluidlyconnected via one or more actuation valves to a source of positive ornegative pneumatic pressure; and a controller configured to control thefluid inlet and outlet valves, the reference chamber valve, and the oneor more actuation valves, and to receive pressure data from a firstpressure sensor connected to the actuation chamber and a second pressuresensor connected to the reference chamber.

The controller is configured to isolate the pumping chamber by closingthe fluid inlet and outlet valves, charge the control chamber with afirst pneumatic pressure; vent the reference chamber or fix a pneumaticpressure in the reference chamber that is different from the controlchamber pneumatic pressure; measure a first control chamber pressure anda first reference chamber pressure, connect the control chamber to thereference chamber by opening the reference chamber valve and equalizingpressures between the control chamber and the reference chamber, measurea third equalized pneumatic pressure in the control and referencechambers. The controller is configured to compute a control chambervolume based on an ideal gas model that assumes the presence of threeclosed mass systems of a gas comprising: a first mass system thatoccupies the control chamber at the end of pressure equalization; asecond mass system that occupies the reference chamber before pressureequalization; and a third mass system that occupies the conduit, a partof the control chamber and a part of the reference chamber afterequalization of pressure begins between the control and referencechambers.

The model can optionally assume an expansion of the first mass systemafter pressure equalization begins, the expansion being modeled as apolytropic process. The model can also assume a compression of thesecond mass system after pressure equalization begins, the compressionbeing modeled as an adiabatic process. The third mass system can bemodeled to be subdivided into component volumes, a first componentvolume occupying part of the control chamber and being modeledpolytropically, a second component volume occupying part of thereference chamber and being modeled adiabatically, and a third componentvolume occupying the conduit and being modeled isothermally.

In another aspect, a system is disclosed for measuring an amount ofliquid in a pumping chamber of a pneumatically actuated diaphragm pump.The system comprises a fluid inlet and fluid outlet valve connected tothe pumping chamber; a diaphragm separating a pneumatically actuatedcontrol chamber from the pumping chamber, the control chamber fluidlyconnected to a reference chamber of known volume via a conduit thatincludes a reference chamber valve; the control chamber fluidlyconnected via one or more actuation valves to a source of positive ornegative pneumatic pressure; and a controller configured to control thefluid inlet and outlet valves, the reference chamber valve, and the oneor more actuation valves, and to receive pressure data from a firstpressure sensor connected to the actuation chamber and a second pressuresensor connected to the reference chamber.

The controller is configured to isolate the pumping chamber by closingthe fluid inlet and outlet valves, charge the control chamber with afirst pneumatic pressure; vent the reference chamber or fix a pneumaticpressure in the reference chamber that is different from the controlchamber pneumatic pressure; measure a first control chamber pressure anda first reference chamber pressure, connect the control chamber to thereference chamber by opening the reference chamber valve and equalizingpressures between the control chamber and the reference chamber, measurea third equalized pneumatic pressure in the control and referencechambers. The controller is configured to compute the control chambervolume based on an ideal gas model that assumes the presence of threeclosed mass systems of a gas comprising: a first mass system thatoccupies the control chamber before pressure equalization; a second masssystem that occupies the reference chamber at the end of pressureequalization; and a third mass system that occupies the conduit, a partof the control chamber and a part of the reference chamber afterequalization of pressure begins between the control and referencechambers.

The model can optionally assume a compression of the first mass systemafter pressure equalization begins, the compression being modeled as apolytropic process. The model can also assume an expansion of the secondmass system after pressure equalization begins, the expansion beingmodeled as an adiabatic process. The third mass system can be modeled tobe subdivided into component volumes, a first component volume occupyingpart of the control chamber being modeled polytropically, a secondcomponent volume occupying part of the reference chamber being modeledadiabatically, and a third component volume occupying the conduit beingmodeled isothermally.

In another aspect, a system is disclosed for measuring an amount ofliquid in a pumping chamber of a pneumatically actuated diaphragm pump.The system comprises a fluid inlet and fluid outlet valve connected tothe pumping chamber; a diaphragm separating a pneumatically actuatedcontrol chamber from the pumping chamber, the control chamber fluidlyconnected to a reference chamber of known volume via a conduit thatincludes a reference chamber valve; the control chamber fluidlyconnected via one or more actuation valves to a source of positive ornegative pneumatic pressure; and a controller configured to control thefluid inlet and outlet valves, the reference chamber valve, and the oneor more actuation valves, and to receive pressure data from a firstpressure sensor connected to the actuation chamber and a second pressuresensor connected to the reference chamber.

The controller is configured to isolate the pumping chamber by closingthe fluid inlet and outlet valves, charge the control chamber with afirst pneumatic pressure; vent the reference chamber or fix a pneumaticpressure in the reference chamber that is different from the controlchamber pneumatic pressure; measure a first control chamber pressure anda first reference chamber pressure, connect the control chamber to thereference chamber by opening the reference chamber valve and equalizingpressures between the control chamber and the reference chamber, measurea third equalized pneumatic pressure in the control and referencechambers. The controller is configured to compute a control chambervolume based on an ideal gas model under a polytropic process, and isconfigured to select a polytropic coefficient for the model using apre-determined function in which the value of the polytropic coefficientdepends on and varies with the control chamber volume.

The pre-determined function can be determined by fixing the controlchamber volume at a known volume, and calculating a polytropiccoefficient corresponding to the known volumes of the control andreference chambers, and the measured first, second and third pressuresbefore and after equalization of pressures. The calculation is repeateda plurality of times, each time corresponding to fixing the controlchamber volume at a different known volume. The function can correspondto a stored look-up table from which the controller selects a polytropiccoefficient corresponding to the volume of the control chamber beingcomputed. Or the function can correspond to an equation that has beenfitted to a plurality of calculated polytropic coefficientscorresponding to a series of known control chamber volumes.

In another aspect, A method for the measuring a volume comprises:providing a chamber defined by one or more rigid impermeable boundariesand one movable impermeable boundary, wherein the volume of the chambervaries; fixing the movable boundary; charging the chamber with a gas toa pre-charge pressure value above ambient pressure and allowing the gasto come to thermal equilibrium with the boundaries of the chamber;recording the pressure in the chamber as the first pressure; releasingthe movable boundary and allowing the gas in the chamber to displace themovable boundary, which displaces a volume of fluid equivalent to thevolume swept by the movable boundary; allowing the gas in the chamber toagain come to thermal equilibrium with the boundaries of the chamber;recording the volume of displaced fluid; recording the pressure in thechamber as the second pressure; and determining the volume of thechamber before displacement based on the first pressure, the secondpressure, the volume of displaced fluid, and an ideal gas model of thechamber gas between the recording of the first pressure and therecording of the second pressure.

The ideal gas model can assume an isothermal process between therecording of the first pressure and the recording of the secondpressure. The method can further comprise determining the volume of thechamber after displacement based on the first pressure, the secondpressure, the volume of displaced fluid and an ideal gas model of thechamber gas between the recording of the first pressure and therecording of the second pressure.

In another aspect, a method is disclosed for calibrating a knownvolume-measurement-procedure comprising: providing a liquid pumpapparatus having a pump chamber separated from a pump control chamber bya movable membrane, and a reference chamber that is fluidly connectableto the pump control chamber, wherein the pump chamber is selectivelyconnected to a liquid volume measurement device; filling the liquid sideof the pump chamber so it occupies most of the pump control chamber;making a first provisional measurement of the pump control chambervolume using a known volume measurement procedure; charging the pumpcontrol chamber with a gas to a pre-charge pressure value and allowingthe gas to come to thermal equilibrium with the boundaries of the pumpcontrol chamber; firstly recording the pressure in the pump controlchamber as the first pressure; connecting the pump to the volumemeasurement device, so that the charge pressure displaces the membrane,which displaces liquid; allowing the gas in the pump control chamber tocome to thermal equilibrium with boundaries of the pump control chamber;recording the volume of displaced fluid measured by the volumemeasurement device; secondly recording the pressure in the pump controlchamber as the second pressure; determining the volume of the pumpcontrol chamber before displacement based on the first pressure, thesecond pressure, the volume of displaced fluid and an ideal gas model ofthe gas in the control chamber between the recording of the firstpressure and the recording of the second pressure; and calculating afirst calibration coefficient based on the volume of the pump controlchamber and the first provisional volume measurement.

The method can further comprise: repeating the steps of making,charging, firstly recording the pressure, connecting, allowing,recording the volume, secondly recording the pressure, and determininguntil substantially all the liquid in pump chamber has been expelled;storing the calibration coefficient and the provisional volumemeasurements as a related pairs; and fitting a calibration equation tothe stored values of calibration coefficient as a function of therelated provisional volume measurements. The accuracy of the determinedvolumes of the pump control chamber can be improved by averaging 1) agiven determined volume, 2) the preceding determined volume plus thepreceding displaced water volume, and 3) the following determined volumeminus the following displaced water volume. The accuracy of the firstdetermined volume of the pump control chamber can also be improved byaveraging 1) the first determined volume, and 2) the followingdetermined volume minus the following displaced water volume. Theaccuracy of the last determined volume of the pump control chamber canalso be improved by averaging 1) the last determined volume, and 2) thepreceding determined volume plus the preceding displaced water volume.

Determining the volume of the pump control chamber can be based on theideal gas model assumes a polytropic process with an expansioncoefficient near 1. The method can further: execute a plurality ofpumping strokes with the liquid pump apparatus, wherein the knownvolume-measurement-procedure occurs after each fill and deliver strokeand the volume of liquid displaced by the liquid pump apparatus isrecorded for each stroke; correcting the volumetric results of the knownvolume-measurement-procedure with the calibration equation; calculatinga volume measurement error based on the corrected volumetric results andthe recorded volume of displaced liquid; re-determining the volumes ofthe pump control chamber before displacement based an ideal gas model,where the polytropic coefficient is adjusted based on the volumemeasurement error; re-calculating the calibration coefficients;re-correcting the volumetric results of the knownvolume-measurement-procedure with the re-calculated calibrationequation; and re-calculating the volume measurement error based on there-corrected volumetric results and the recorded volume of displacedliquid.

In another aspect, a system is disclosed for measuring an amount ofliquid in a pumping chamber of a pneumatically actuated diaphragm pumpcomprising: a fluid inlet and fluid outlet valve connected to thepumping chamber; a diaphragm separating a pneumatically actuated controlchamber from the pumping chamber, the control chamber fluidly connectedto a reference chamber of known volume via a conduit that includes areference chamber valve; the control chamber fluidly connected via oneor more actuation valves to a source of positive or negative pneumaticpressure; a controller configured to control the fluid inlet and outletvalves, the reference chamber valve, and the one or more actuationvalves, and to receive pressure data from a first pressure sensorconnected to the actuation chamber and a second pressure sensorconnected to the reference chamber; wherein the controller is configuredto isolate the pumping chamber by closing the fluid inlet and outletvalves, charge the control chamber with a first pneumatic pressure; ventthe reference chamber or fix a pneumatic pressure in the referencechamber that is different from the control chamber pneumatic pressure;measure a first control chamber pressure and a first reference chamberpressure, connect the control chamber to the reference chamber byopening the reference chamber valve and equalizing pressures between thecontrol chamber and the reference chamber, measure a third equalizedpneumatic pressure in the control and reference chambers, and compute acontrol chamber volume based on an ideal gas model under a polytropicprocess, wherein the controller is configured to select a polytropiccoefficient for the model using a pre-determined function in which thevalue of the polytropic coefficient depends on and varies with anestimate of the control chamber volume that is calculated from the firstcontrol chamber pressure, the first reference chamber pressure and thethird equalized pressure based on an ideal gas model.

The pre-determined function optionally can be determined by fixing thecontrol chamber volume at a known volume, and calculating the estimateof the control chamber volume and a polytropic coefficient correspondingto the known volumes of the control and reference chambers, and themeasured first, second and third pressures before and after equalizationof pressures; wherein said calculation is repeated a plurality of times,each said time corresponding to fixing the control chamber volume at adifferent known volume. The function can correspond to a stored look-uptable from which the controller selects a polytropic coefficientcorresponding to the estimate of control chamber volume being computed.The function can also correspond to an equation that has been fitted toa plurality of calculated polytropic coefficients corresponding to aseries of estimated control chamber volumes.

In another aspect, a system is disclosed for measuring an amount ofliquid in a pumping chamber of a pneumatically actuated diaphragm pumpcomprising: a fluid inlet and fluid outlet valve connected to thepumping chamber; a diaphragm separating a pneumatically actuated controlchamber from the pumping chamber, the control chamber fluidly connectedto a reference chamber of known volume via a conduit that includes areference chamber valve; the control chamber fluidly connected via oneor more actuation valves to a source of positive or negative pneumaticpressure; a controller configured to control the fluid inlet and outletvalves, the reference chamber valve, and the one or more actuationvalves, and to receive pressure data from a first pressure sensorconnected to the actuation chamber and a second pressure sensorconnected to the reference chamber; wherein the controller is configuredto isolate the pumping chamber by closing the fluid inlet and outletvalves, charge the control chamber with a first pneumatic pressure; ventthe reference chamber or fix a pneumatic pressure in the referencechamber that is different from the control chamber pneumatic pressure;measure a first control chamber pressure and a first reference chamberpressure, connect the control chamber to the reference chamber byopening the reference chamber valve and equalizing pressures between thecontrol chamber and the reference chamber, measure a third equalizedpneumatic pressure in the control and reference chambers, and compute acontrol chamber volume based on an ideal gas model under a polytropicprocess, wherein the controller is configured to select a polytropiccoefficient for the model using a pre-determined function in which thevalue of the polytropic coefficient depends on and varies with thecontrol chamber volume.

The pre-determined function optionally can be determined by fixing thecontrol chamber volume at a known volume, and calculating a polytropiccoefficient corresponding to the known volumes of the control andreference chambers, and the measured first, second and third pressuresbefore and after equalization of pressures; wherein said calculation isrepeated a plurality of times, each said time corresponding to fixingthe control chamber volume at a different known volume. The function cancorrespond to a stored look-up table from which the controller selects apolytropic coefficient corresponding to the volume of the controlchamber being computed. The function can also correspond to an equationthat has been fitted to a plurality of calculated polytropiccoefficients corresponding to a series of known control chamber volumes.

In another aspect, a method is disclosed for calibrating a known volumemeasurement procedure of claim 2a, wherein the accuracy of thedetermined volumes of the pump control chamber are improved byaveraging 1) a given determined volume, 2) the preceding determinedvolume plus the preceding displaced water volume, and 3) the followingdetermined volume minus the following displaced water volume.

In another aspect, a system is disclosed for calculating a change influid volume in a pumping chamber of a pneumatically actuated diaphragmpump using a gas having a heat capacity ratio of n. The system comprisesa control chamber separated from the pumping chamber by a flexiblediaphragm; a fluid inlet or outlet of the pumping chamber; a valveconnecting the control chamber to a pressurized source of the gas; apressure sensor fluidly connected to the control chamber; and acontroller that receives pressure data from the pressure sensor, thatcontrols the valve, and that is configured to regulate pressure in thecontrol chamber by opening or closing the valve. The controller isconfigured to compute a change in volume of the control chamber as fluidenters or leaves the pumping chamber by monitoring a pressure change inthe control chamber when the valve is closed. This computation assigns afirst chamber volume to a first measured pressure, and calculates asecond chamber volume based on a second later measured pressure using anequation in which a ratio of the second measured pressure to the firstmeasured pressure is assumed to be equal to a ratio of the first chambervolume to the second chamber volume, raised to a power between 1 and n.

The assigned first chamber volume can be derived from an initialcondition in which the control chamber is pressurized with air, thepumping chamber and control chamber are isolated, a measurement ofcontrol chamber pressure is taken, the control chamber is connected to areference chamber having a known volume and measured pressure, and thecontroller derives an initial volume of the control chamber using amodel based on an ideal gas equation. The controller can calculate athird chamber volume as fluid continues to enter or leave the pumpingchamber by assigning the second chamber volume to the second measuredpressure and calculating a third chamber volume based on a thirdmeasured pressure using an equation in which a ratio of the thirdmeasured pressure to the second measured pressure is assumed to be equalto a ratio of the second chamber volume to the third chamber volume,raised to a power between 1 and n. The controller can calculate a fluidflow into or out of the pumping chamber based on a difference betweenthe first, second and third chamber volumes. The controller can repeatthe calculations periodically during a time period in which fluidcontinues to enter or leave the pumping chamber, and can suspend thecalculations during a time period in which the valve is opened toconnect the control chamber with the pressurized source of the gas. Thepressurized source of the gas can be a positively pressurized source ora negatively pressurized source. The gas can be air. The value of n canbe approximately 1.4. The value of n can be adjusted by the controllerby comparing a cumulative calculated volume of fluid moved into or outof the pumping chamber during a pump stroke to a volume change in thepumping chamber calculated from an initial volume determination at abeginning of the pump stroke and a final volume determination at an endof the pump stroke.

In another aspect, a method is disclosed for determining an amount offluid delivered by a diaphragm pump having a pumping chamber separatedfrom a pneumatically actuated control chamber by a diaphragm, and havingpneumatically actuated inlet and outlet valves. The method isimplemented by a controller that closes the outlet valve, opens theinlet valve, and connects the control chamber to a negative pressuresource to apply negative pneumatic pressure to the diaphragm pump todraw fluid into the pumping chamber. The controller closes the inletvalve, connects the control chamber to the positive pressure source,isolates the control chamber, measures a first control chamber pressure,measures a first reference chamber pressure in a reference chamberhaving a known volume, connects the control chamber to the referencechamber, and calculates a first volume of the control chamber. It thenopens the outlet valve, and connects the control chamber to a positivepressure source to apply a positive pneumatic pressure to the diaphragmpump to expel fluid from the pumping chamber. It then closes the outletvalve; vents the control chamber to reduce pressure in the controlchamber toward atmospheric pressure; connects the control chamber to thepositive pressure source, isolates the control chamber, measures asecond control chamber pressure, measures a second reference chamberpressure, connects the control chamber to the reference chamber, andcalculates a second volume of the control chamber; and then determinesthe amount of fluid delivered by the diaphragm pump based on the firstand second volumes of the control chamber.

In another aspect, a method is disclosed for determining an amount offluid delivered by a pumping cassette comprising a first and a seconddiaphragm pump each said diaphragm pump having a pumping chamberseparated from a pneumatically actuated control chamber by a diaphragm,and each having pneumatically actuated inlet and outlet valves, themethod comprising having a controller perform for each of diaphragmpumps the steps of: closing the outlet valve, opening the inlet valve,and connecting the control chamber to a negative pressure source toapply negative pneumatic pressure to the diaphragm pump to draw fluidinto the pumping chamber; closing the inlet valve, connecting thecontrol chamber to the positive pressure source, isolating the controlchamber, measuring a first control chamber pressure, measuring a firstreference chamber pressure in a reference chamber having a known volume,connecting the control chamber to the reference chamber, and calculatinga first volume of the control chamber; opening the outlet valve, andconnecting the control chamber to a positive pressure source to apply apositive pneumatic pressure to the diaphragm pump to expel fluid fromthe pumping chamber; closing the outlet valve; venting the controlchamber to reduce pressure in the control chamber toward atmosphericpressure; connecting the control chamber to the positive pressuresource, isolating the control chamber, measuring a second controlchamber pressure, measuring a second reference chamber pressure,connecting the control chamber to the reference chamber, and calculatinga second volume of the control chamber; and determining the amount offluid delivered by the diaphragm pump based on the first and secondvolumes of the control chamber. Expelling fluid from the pumping chamberof the second diaphragm pump is performed after the control chamber ofthe first diaphragm pump is vented, and expelling fluid from the pumpingchamber of the first diaphragm pump is performed after the controlchamber of the second diaphragm pump is vented.

In another aspect, a system is disclosed for measuring a volume ofliquid in a pumping chamber of a peritoneal dialysis pump cassettecomprising: a base unit in which the pump cassette can be installed, thebase unit including a control block having a control chamber depressionconfigured to mate with the pumping chamber of the pumping cassette, andto move a flexible diaphragm between the pumping chamber and the controlchamber under positive or negative pneumatic pressure. The controlchamber depression is in communication via one or more pump actuationvalves in the base unit with a source of positive or negative pressure,and in communication via a vent valve in the base unit with a ventconnected to atmospheric pressure. A controller is configured to controlthe one or more pump actuation valves to operate the pumping cassette tofill the pumping chamber with liquid and to deliver liquid from thepumping chamber. The controller is configured to control one or morepneumatically actuated membrane inlet and outlet valves in the pumpcassette via one or more inlet and outlet actuation valves in the baseunit connected to the source of positive or negative pneumatic pressure.The controller is also configured to measure pneumatic pressure in thecontrol chamber via a pressure sensor, and to calculate a volume ofliquid in the pumping chamber, the calculation involving pneumaticallypressurizing the control chamber before taking a pressure measurement.The controller is also configured to connect the control chamber withthe vent after commanding a liquid delivery stroke of the pump cassetteand before pneumatically pressurizing the control chamber to perform apumping chamber liquid volume calculation.

In another aspect, a system is disclosed for adjusting negative pressureused to withdraw fluid from a cavity of a patient, the systemcomprising: a pump configured to provide negative pressure to a fluidline connected to the cavity; a controller configured to measure andcontrol the negative pressure provided by the pump. The controller isalso configured to measure a rate of flow of fluid from the fluid lineto the pump. The controller is arranged to control the pump by providinga first negative pressure to the fluid line, measuring the rate of fluidflow, and control the pump by providing a second negative pressure tothe fluid line that is greater in magnitude than the first negativepressure if the measured rate of fluid flow exceeds a pre-determinedvalue.

A system is also disclosed for adjusting negative pressure used towithdraw fluid from a cavity of a patient. The system comprises: a pumpconfigured to provide negative or positive pressure to a fluid lineconnected to the cavity; a controller configured to measure and controlthe pressure provided by the pump. The controller is also configured tomeasure a rate of flow of fluid from the fluid line to the pump, so thatthe controller is arranged to control the pump by providing negativepressure to the fluid line, measuring the rate of fluid flow, andcontrol the pump by providing a positive pressure to the fluid line ifthe measured rate of fluid flow is less than a pre-determined value, andwherein the controller is arranged to re-apply negative pressure to thefluid line if a measured fluid flow upon application of the positivepressure is greater than a pre-determined amount.

A system is also disclosed for adjusting negative pressure used towithdraw fluid from a cavity of a patient, the system comprising: a pumpconfigured to provide negative pressure to a fluid line connected to thecavity; a controller configured to measure and control the pressureprovided by the pump. The controller is also configured to measure aflow rate of fluid from the fluid line to the pump. The controller isthen arranged to control the pump by providing negative pressure in anamount that varies continuously as a function of the measured flow rateof the fluid, such that the variation in negative pressure applied bythe pump is limited to within a pre-determined range of negativepressures.

A system is also disclosed for adjusting negative pressure used towithdraw fluid from a cavity of a patient, the system comprising: a pumpconfigured to provide negative pressure to a fluid line connected to thecavity; a controller configured to measure and control the pressureprovided by the pump; the controller also being configured to measure aflow rate of fluid from the fluid line to the pump. A user interface isconfigured to provide a user a measure of the negative pressure appliedby the pump, and configured to receive input from the user to adjust theamount of negative pressure applied by the pump, such that thecontroller is arranged to receive via the user interface a command fromthe user to adjust the negative pressure applied by the pump, and toeffectuate the adjustment.

A system is also disclosed for adjusting negative pressure used towithdraw fluid from a cavity of a patient, the system comprising: a pumpconfigured to provide negative pressure to a fluid line connected to thecavity; a controller configured to measure and control the pressureprovided by the pump; the controller also configured to measure a flowrate of fluid from the fluid line to the pump, and to compute a pumpingduration based on the measured flow rate. A user interface is configuredto provide a user a measure of the negative pressure applied by thepump, and configured to receive input from the user to adjust the amountof negative pressure applied by the pump, such that the controller isarranged to receive via the user interface a command from the user toadjust the negative pressure applied by the pump, to compute a change inthe pumping duration resulting from the adjustment, to displayinformation about the change in pumping duration on the user interface,and to receive from the user a command to proceed or not proceed withthe adjustment.

In another aspect, a system is disclosed for performing automatedperitoneal dialysis comprising; a cycler comprising a fluid pump andcontroller, the controller configured to measure and control an amountof fluid pumped to a peritoneal cavity and to track a remaining volumeof the fluid in a solution bag. The controller is configured to: controla dialysis therapy by administering a pre-determined number of therapycycles, each therapy cycle comprising a fill phase, dwell phase anddrain phase; and maintain a pre-determined minimum volume ofintra-peritioneal fluid during the dwell phase. It is also configured tocancel a final therapy cycle if a calculated final volume of fluidremaining in the solution bag for the final therapy cycle is less than avolume required to maintain the minimum intra-peritoneal fluid volumefor the final therapy cycle dwell phase; divide the remaining finalvolume of fluid in the solution bag among a remaining number of therapycycle fill volumes; and divide a duration of the final therapy cycledwell phase among a remaining number of therapy cycle dwell phases. Thecontroller is also configured to further adjust the fill volumes of theremaining number of therapy cycles, or the duration of the dwell phasesof the remaining number of therapy cycles to prevent an accumulation ofintra-peritoneal fluid during the remaining therapy cycles fromexceeding a pre-determined maximum intra-peritoneal volume of fluid.

In another aspect, a system in an automated peritoneal dialysisapparatus is disclosed for replenishing a heater bag with fluid during adialysis therapy comprising a fluid fill phase, a fluid dwell phase, anda fluid drain phase. The system comprises a controller configured to:track a remaining volume of fluid remaining in the heater bag; compute areplenish volume of fluid to be infused into the heater bag comprisingsubtracting the remaining volume from a fill volume of fluid to beinfused into a patient in a subsequent fill phase of the dialysistherapy; compute a replenish volume transfer time required to transferthe replenish volume from a fluid source to the heater bag; compute areplenish volume heating time required to heat the replenish volume towithin a pre-determined range of a pre-determined temperature set point;and compute a remaining dwell time required to complete the fluid dwellphase. The controller is also configured to control a fluid heater ofthe peritoneal dialysis apparatus to heat the replenish fluid as itenters the heater bag, and to control a fluid pump of the peritonealdialysis apparatus to initiate pumping of the replenish volume to theheater bag when the remaining dwell time is equal to or greater than thegreater of the replenish volume transfer time or the replenish volumeheating time.

In another aspect, a system for replenishing a fluid heater bag of amedical fluid delivery apparatus is disclosed, the system comprising: aprocessor configured to receive temperature data associated with a fluidin the heater bag, to control a heater to heat the fluid in the heaterbag, to control a fluid pump to pump the fluid in a replenish operationinto the heater bag from a fluid source, to pump the fluid in a fillphase out of the heater bag to a patient, to control a dwell phaseduring which the fluid remains in the patient, and to pump the fluid ina drain phase out of the patient to a destination. The controller isfurther configured to determine a replenish volume to be transferred tothe heater bag during the replenish operation, the replenish volumedetermination made by subtracting the volume of fluid in the bag at thebeginning of the replenish operation from a volume of fluid to be pumpedto the patient in the next fill phase; compute a replenish volumetransfer time required to transfer the replenish volume from the fluidsource to the heater bag; compute a replenish volume heating timerequired to heat the fluid to within a pre-determined range of apre-determined temperature set point; compute a drain time required tocomplete the drain phase; and control the fluid pump to initiate pumpingof the fluid in the replenish operation at a remaining dwell time duringthe dwell phase that is approximately equal to the greater of (1) thedrain time plus the replenish volume heating time or (2) the drain timeplus the replenish volume transfer time.

In another aspect, a solution expiration timing system is disclosed foran automated dialysis apparatus connected to a first fluid reservoir anda fluid heating reservoir. The system comprises a controller configuredto begin a first solution expiration timer when a fluid is pumped fromthe first fluid reservoir to the fluid heating reservoir; begin a secondsolution expiration timer when the fluid in the fluid heating reservoirachieves a pre-determined temperature; wherein the controller isconfigured to declare a first expiration time when a firstpre-determined time interval has elapsed, and to declare a secondexpiration time when a second pre-determined time interval has elapsed;and wherein the controller stops fluid transfer from the first fluidreservoir to the fluid heating reservoir at the first expiration time,and stops fluid transfer from the fluid heating reservoir to a user atthe second expiration time.

In another aspect, a solution expiration timing system is disclosed foran automated dialysis apparatus connected to a first fluid reservoircontaining a first fluid and a second fluid reservoir containing asecond fluid. The system comprises a controller configured to: begin afirst solution expiration timer when the first fluid is pumped from thefirst fluid reservoir to a fluid heating reservoir; begin a secondsolution expiration timer when the second fluid is pumped from thesecond fluid reservoir to the fluid heating reservoir; wherein thecontroller is configured to declare a first expiration time when a firstpre-determined time interval has elapsed, and to declare a secondexpiration time when a second pre-determined time interval has elapsed;and wherein the controller stops fluid transfer from the first fluidreservoir to the fluid heating reservoir at the first expiration time,and stops fluid transfer from the second fluid reservoir to the fluidheating reservoir at the second expiration time.

In another aspect, a system is disclosed for detecting that a fluid lineis primed with liquid. The system comprises a fluid pump having apumping chamber configured to pump a liquid from a proximal portion to adistal portion of the fluid line at a pre-determined pressure; a sensorconfigured to measure the flow of liquid in the fluid line or to measurepressure in the pumping chamber to determine the flow of liquid in thefluid line; and a controller configured to receive data from the sensorand to compare the flow of liquid or a change in the flow of liquid inthe fluid line with a pre-determined value. The distal portion of thefluid line comprises a flow restrictor that measurably reduces the flowof liquid in the fluid line when air in the distal portion of the fluidline is replaced by the liquid being pumped by the pump; and thecontroller declares the fluid line to be primed when the reduction inmeasured liquid flow reaches the predetermined value.

In another aspect, an automated peritoneal dialysis cycler is equippedwith an autoconnect apparatus for spiking solution lines for dialysistherapy. A cap detection system is disclosed for detecting the presenceof a solution line or spike cap on a cap stripper, the cap detectionsystem comprising: a position sensor for the cap stripper configured todetect a position of the cap stripper relative to a plane in which aplurality of cassette spikes or a plurality of solution lines residewhen placed in the cycler; a controller configured to command movementof the cap stripper toward or away from the plane, or laterally in adirection parallel with the plane, and to receive information from theposition sensor to compare the position of the cap stripper relative toa first or second pre-determined fully deployed position of the capstripper toward the plane. The controller is configured to: command thecap stripper to move toward the plane when one or more solution linesare installed in the cycler, and to issue an alert if a cap on the capstripper prevents a final position of the cap stripper from reaching thefirst pre-determined fully deployed position; or command the capstripper to move laterally a pre-determined distance and then toward theplane when no solution lines are installed in the cycler, and to issuean alert if a cap on the cap stripper prevents a final position of thecap stripper from reaching the second pre-determined fully deployedposition.

In another aspect, an identification system is disclosed for a fluidline connected to a fluid container for medical use. The systemcomprises an image sensor configured to read an image generated byfluorescent light, the image comprising a pattern of coded informationcharacterizing the fluid in the container; a fluid line mount configuredto hold the fluid line in a fixed position within a field of view of theimage sensor; an identification tag attached to a portion of the fluidline on or near the mount; the identification tag having an identifyingmarking arranged to emit fluorescent light in the pattern of the imagein response to absorption of light having a non-visible wavelength; anemitter configured to emit light in the non-visible wavelength onto theidentification tag; and a controller configured to receive an electronicsignal from the image sensor and to decode the information in the imagepattern emitted by the identifying marking of the identification tag.

In another aspect, a brace is disclosed for a distal portion of a fluidline, the fluid line configured to receive a hollow spike in a fluidhandling apparatus, the brace comprising: a rigid clamping memberconfigured to encircle the distal portion of the fluid line after beingmounted on the distal portion of the fluid line, having one or morefeatures on an inside surface of the clamping member configured tocooperate with one or more complementary features on an outside surfaceof the distal portion of the fluid line. The brace is arranged to bemountable on the distal portion of the fluid line to constrain it frombending out of alignment with a longitudinal axis of the hollow spikebefore or after an initiation of a spiking of the distal portion of thefluid line.

In another aspect, an electronic circuit is disclosed for reducing touchor leakage current from a heating element of an automated peritonealdialysis apparatus. The circuit comprises: a first relay connecting afirst pole of an AC mains source to a first end of the heating element;a second relay connecting a second pole of the AC mains source to asecond end of the heating element; and a controller configured tocontrol current delivery to the heating element by transmitting an onsignal to both the first and second relays or an off signal to both thefirst and second relays, the on signal causing AC mains current to flowthrough the heating element, and the off signal preventing AC mainscurrent from flowing through the heating element. The heating element isisolated from AC mains voltage when the controller transmits an offsignal.

In another aspect, an electronic circuit is disclosed for deliveringelectric power to an automated peritoneal dialysis apparatus from apower source having a first voltage or a higher second voltage, theelectronic circuit comprising: a heater comprising a first heaterelement connected to a second heater element by a heater select relay,the heater select relay configured to connect the first heater elementeither in series or in parallel with the second heater element; acurrent sense element configured to measure a current flow through theheater; a controller configured to set a default configuration of theheater select relay on powering up so that the first heater element isin series with the second heater element; wherein the controller isprogrammed to receive information on current flow from the current senseelement, and is programmed to command the heater select relay to set thefirst heater element in parallel with the second heater element if ameasured current is less than a pre-determined target current for theheater.

In another aspect, a control system is disclosed for a heater of anautomated peritoneal dialysis apparatus comprising: a resistive heatingelement; a solid state relay connecting an electrical power source tothe heating element; a first processor configured to generate and send apulse width modulated signal to a gating circuit; a second processorconfigured to generate and send a safety signal to the gating circuit;wherein the gating circuit is configured to reproduce or transmit thepulse width modulated signal to operate the solid state relay if thesafety signal is in a first mode, and is configured to prevent theoperation of the solid state relay if the safety signal is in a secondmode.

The gating circuit optionally can operate the solid state relay throughoptical transmission. The optical transmission can be performed using alight emitting diode of an opto-isolator. The solid state relay cancomprise a triac or a pair of silicon controlled rectifiers. The solidstate relay can connects a first pole of an AC mains voltage source tothe heating element, and a second solid state relay connects a secondpole of the AC mains voltage source to the heating element, such thatthe pulse width modulated signal reproduced or transmitted by the gatingcircuit operates both the solid state relay and the second solid staterelay. The solid state relay can also connect a first pole of an ACmains voltage source to the heating element, and a second solid staterelay connects a second pole of the AC mains voltage source to theheating element, such that a second gating circuit is configured toreceive the pulse width modulated signal from the first processor andthe safety signal from the second processor, and such that the secondgating circuit is configured to reproduce or transmit the pulse widthmodulated signal to operate the second solid state relay if the safetysignal is in the first mode, and is configured to prevent the operationof the second solid state relay if the safety signal is in the secondmode.

In another aspect, a housing is disclosed for an automated peritonealdialysis apparatus comprising: a dual pressure reservoir integrallyformed in the housing, the dual pressure reservoir having a firstsection separated from a second section by a dividing wall; the firstsection configured for positive air pressurization by a pump via a firstport; the second section configured for negative air pressurization bythe pump via a second port; and a cover plate for enclosing the firstand second sections, said cover plate forming a seal against a perimeterwall of the first section, a perimeter wall of the second section, andthe dividing wall between the first and second sections.

A housing is also disclosed for an automated peritoneal dialysisapparatus that comprises: a dual pressure reservoir integrally formed inthe housing, the dual pressure reservoir having a first sectionseparated from a second section by a dividing wall; the first sectionconfigured for positive air pressurization by a pump via a first port,and comprising a first perimeter wall joining with the dividing wall anda first set of one or more stiffening members extending from a portionof the first perimeter wall to the dividing wall; the second sectionconfigured for negative air pressurization by the pump via a secondport, and comprising a second perimeter wall joining with the dividingwall and a second set of one or more stiffening members extending from aportion of the second perimeter wall to the dividing wall; and a coverplate for enclosing the first and second sections, said cover plateforming a seal against the first and second perimeter walls and thedividing wall between the first and second sections.

A housing is also for an automated peritoneal dialysis apparatuscomprising: a dual pressure reservoir integrally formed in the housing,the dual pressure reservoir having a first section separated from asecond section by a dividing wall; the first section configured forpositive air pressurization by a pump via a first port, and comprising afirst perimeter wall joining with the dividing wall; the second sectionconfigured for negative air pressurization by the pump via a secondport, and comprising a second perimeter wall joining with the dividing;and a cover plate for enclosing the first and second sections, saidcover plate forming a seal against the first and second perimeter wallsand the dividing wall between the first and second sections; such that aplurality of stiffening members are attached to an inside surface of thecover plate, so that when the cover plate is attached to the dualpressure reservoir, a first set of said stiffening members extends inthe first section from a portion of the first perimeter wall to thedividing wall, and a second set of said stiffening members extends inthe second section from a portion of the second perimeter wall to thedividing wall.

A housing is also disclosed for a dual pressure air reservoircomprising: a first reservoir surrounding a second reservoir, the firstand second reservoirs separated by a dividing wall, and the firstreservoir having an outer perimeter wall; the first reservoir configuredfor negative air pressurization by a pump via a first port; the secondreservoir configured for positive air pressurization by the pump via asecond port; a cover plate for enclosing the first and secondreservoirs, said cover plate forming a seal against the outer perimeterwall of the first reservoir and the dividing wall between the first andsecond reservoirs; such that a surface area of the cover plate definedby outer perimeter wall and the dividing wall is greater than a surfacearea of the cover plate defined by an area within the dividing wall; andsuch that a depth of the second reservoir is greater than a depth of thefirst reservoir so that a volume of the first reservoir is approximatelyequal to a volume of the second reservoir.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the invention are described below with reference toillustrative embodiments that are shown, at least in part, in thefollowing figures, in which like numerals reference like elements, andwherein:

FIG. 1 shows a schematic view of an automated peritoneal dialysis (APD)system that incorporates one or more aspects of the invention;

FIG. 1A shows an alternative arrangement for a dialysate delivery setshown in FIG. 1;

FIG. 2 is a schematic view of an illustrative set for use with the APDsystem of FIG. 1;

FIG. 3 is an exploded perspective view of a cassette in a firstembodiment;

FIG. 4 is a cross sectional view of the cassette along the line 4-4 inFIG. 3;

FIG. 5 is a perspective view of a vacuum mold that may be used to form amembrane having pre-formed pump chamber portions in an illustrativeembodiment;

FIG. 6 shows a front view of the cassette body of FIG. 3;

FIG. 7 is a front view of a cassette body including two different spacerarrangements in an illustrative embodiment;

FIG. 8 is a rear perspective view of the cassette body of FIG. 3;

FIG. 9 is a rear view of the cassette body of FIG. 3;

FIG. 10 is a front perspective view of an exemplary configuration of afluid line state detector or liquid level detector;

FIG. 11 is a rear perspective view of a fluid line state detector orliquid level detector;

FIG. 12 is a perspective layout view of three LEDs and an opticaldetector surface-mounted on a printed circuit board;

FIG. 13 is a plan view of three LEDs and an optical detector mounted ona detector circuit board;

FIG. 14 is an exploded perspective view of the detector of FIG. 10showing the printed circuit board and transparent or translucent plasticinsert;

FIG. 15 is a graph showing the ability of the liquid level detector ofFIG. 10 to distinguish between a primed and a non-primed fluid line;

FIG. 16 is a graph showing measurements collected by an optical sensorcomparing liquid detection using an orthogonally oriented LED vs. anangled LED;

FIG. 17 is a graph showing the ability of the liquid level detector ofFIG. 10 to distinguish between the presence and absence of a tubingsegment within the detector;

FIG. 18 is a graph showing the range of signals corresponding to aprimed and a non-primed fluid line for different cyclers using theliquid detector of FIG. 10;

FIG. 19 is a perspective view of an alternative configuration of aliquid level detector;

FIG. 20 and FIG. 21 show an embodiment of a fluid line cap, fluid line,and a fluid line connector;

FIG. 22 and FIG. 23 show another embodiment of a fluid line cap, fluidline, and a fluid line connector;

FIG. 24 shows an example of a fluid line cap including a notch;

FIG. 25 shows an example of a fluid line cap including a restriction;

FIG. 26 shows a cross section of a fluid line cap taken at line 26-26 ofFIG. 25;

FIG. 27 shows an example of a fluid line cap installed on a fluid lineconnector of a fluid line;

FIG. 28 shows a cross section of the fluid line cap, fluid line, andfluid line connector of FIG. 27 taken at line 28-28 of FIG. 27;

FIG. 29 shows a flowchart outlining a number of steps which may be usedby a cycler to prime a line with a two part prime;

FIG. 30 is a perspective view of the front of an unloaded organizer(absent any solution lines);

FIG. 31 is a back view of the organizer of FIG. 30;

FIG. 32 is a perspective view of an organizer including a plurality ofsolution lines, a fluid line, and a drain line;

FIG. 33 is a perspective view of an organizer clip;

FIG. 34 is a perspective view of an organizer clip receiver;

FIG. 35 is a perspective view of a door latch sensor assembly associatedwith a cycler;

FIG. 36 is a cross-sectional view of the door latch sensor assembly ofFIG. 35;

FIG. 37 is a perspective view of the APD system of FIG. 1 with the doorof the cycler in an open position;

FIG. 38 is a perspective view of the inner side of the door of thecycler show in FIG. 37;

FIG. 39 is a perspective view of a carriage in a first embodiment;

FIG. 40 is an enlarged perspective view of a solution line loaded intothe carriage of FIG. 39;

FIG. 41 is a perspective view of an open identification tag;

FIG. 42 is a perspective view of a carriage drive assembly including anAutoID camera mounted to an AutoID camera board;

FIG. 43 shows a flowchart outlining a number of steps which may be usedto determine information about a set to be installed in a cycler;

FIG. 44 shows a system including an identification tag having a codeprinted in a fluorescent material;

FIG. 45 shows an example screen depicting a result of an identificationtag analysis generated for display on a user interface;

FIG. 46 shows an example brace for a solution line in an unassembledposition on the solution line;

FIG. 47 is a perspective view of an example brace for a solution line;

FIG. 48 shows another example brace for a solution line in anunassembled position on the solution line;

FIG. 49 is a perspective view of an example brace for a solution line;

FIG. 50 is a perspective view of an example brace for a solution line;

FIG. 51 shows an example brace for a solution line coupled in place onthe solution line;

FIG. 52 is a cross-sectional view taken at the medial plane of asolution line which shows a brace in place around the solution line;

FIG. 53 shows an embodiment of a carriage which includes clip sectionsconfigured to accept a solution line about which a brace is installed;

FIG. 54 shows a detailed view of region BQ of FIG. 53;

FIG. 55 is a perspective view of a carriage including a number ofsolution line clips or retaining elements;

FIG. 56 shows a detailed view of region BS of FIG. 55;

FIG. 57 is a close up cross-section view of a portion of a cycler whichincludes a carriage and other components;

FIG. 58 is a right front perspective view of a carriage drive assemblyand cap stripper in a first embodiment;

FIG. 59 a left front perspective view of the carriage drive assembly andcap stripper of FIG. 58;

FIG. 60 is a rear perspective view of the carriage drive assembly;

FIG. 61 is a left rear perspective view of a carriage drive assembly andcap stripper in a second illustrative embodiment;

FIG. 62 is another left rear perspective view of the carriage driveassembly and cap stripper of FIG. 61;

FIG. 63A is a left front perspective view of the cap stripper element ofFIG. 62;

FIG. 63B is a right front perspective view of the cap stripper elementof FIG. 62;

FIG. 64 is a front view of the cap stripper element of FIG. 62;

FIG. 65 is a cross sectional view along the line 65-65 in FIG. 64;

FIG. 66 is a cross sectional view along the line 66-66 in FIG. 64;

FIG. 67 is a cross sectional view along the line 67-67 in FIG. 64;

FIG. 68 is a perspective view of an embodiment for a stripper element ofa cap stripper;

FIG. 69 is a front perspective view of the carriage drive assembly ofFIG. 42 showing the position of the stripper element of FIG. 68 withinthe carriage drive assembly;

FIG. 70A is a perspective view of a portion of the stripper element ofFIG. 68, in which a spike cap is positioned;

FIG. 70B is a perspective view of a portion of the stripper element ofFIG. 68, in which a solution line cap is positioned over a spike cap;

FIG. 70C is a perspective view of a portion of the stripper element ofFIG. 68, showing a sensor element and rocker arm in the absence of aspike cap;

FIG. 71 is a close-up exploded view of the connector end of a solutionline in an illustrative embodiment;

FIG. 72 is a schematic view of a cassette and solution lines beingloaded into the cycler of FIG. 37;

FIG. 73 is a schematic view of the cassette and solution lines afterplacement in respective locations of the door of the cycler of FIG. 37;

FIG. 74 is a schematic view of the cassette and solution lines after thedoor of the cycler is closed;

FIG. 75 is a schematic view of the solution lines being engaged withspike caps;

FIG. 76 is a schematic view of the cap stripper engaging with spike capsand solution line caps;

FIG. 77 is a schematic view of the solution lines with attached caps andspike caps after movement away from the cassette;

FIG. 78 is a schematic view of the solution lines after movement awayfrom the solution line caps and spike caps;

FIG. 79 is a schematic view of the cap stripper retracting with thesolution line caps and spike caps;

FIG. 80 is a schematic view of the solution lines being engaged with thespikes of the cassette;

FIG. 81 depicts a flowchart detailing a number of example steps whichmay be used to detect the presence of leftover caps in a cap stripper;

FIG. 82 depicts an example screen which may be generated for display ona user interface of a cycler by a processor of the cycler the displaysinstructions on how to remove caps from a cap stripper;

FIG. 83 depicts an example screen which may be generated for display ona user interface of a cycler by a processor of the cycler that displaysinstructions on how to remove caps from a cap stripper;

FIG. 84 is a cross sectional view of a cassette with five stages of asolution line connection operation shown with respect to correspondingspikes of the cassette;

FIG. 85 is a rear view of a cassette in another illustrative embodimentincluding different arrangements for a rear side of the cassetteadjacent the pump chambers;

FIG. 86 is an end view of a spike of a cassette in an illustrativeembodiment;

FIG. 87 is a perspective view of an alternative embodiment of the spikesof a cassette;

FIG. 88 shows an embodiment of a spike cap configured to fit over thespikes shown in FIG. 87;

FIG. 89 is a cross-sectional view of a spike cap shown in FIG. 88;

FIG. 90 is a front view of a control surface of the cycler forinteraction with a cassette in the FIG. 37 embodiment;

FIG. 91 is a front view and selected cross-sectional views of anembodiment of a control surface of the cycler;

FIG. 92 is an exploded view of an assembly for the interface surface ofFIG. 90, with the mating pressure delivery block and pressuredistribution module;

FIG. 93 is an exploded view of the integrated manifold;

FIG. 94 shows two isometric views of the integrated manifold;

FIG. 95 shows a schematic of the pneumatic system that controls fluidflow through the cycler;

FIG. 96 is a front side view of an embodiment of a cassette fixture;

FIG. 97 shows another example of a cassette fixture which is made from amodified cassette such as the cassette shown in FIG. 3;

FIG. 98 shows another example of a cassette fixture which is made from amodified cassette;

FIG. 99 is an exploded perspective view of an occluder in anillustrative embodiment;

FIG. 100 is a partially exploded perspective view of the occluder ofFIG. 99;

FIG. 101 is a top view of the occluder of FIG. 99 with the bladder in adeflated state;

FIG. 102 is a top view of the occluder of FIG. 99 with the bladder in aninflated state;

FIG. 103 is a schematic view of a pump chamber of a cassette andassociated control components and inflow/outflow paths in anillustrative embodiment;

FIG. 104 is a plot of illustrative pressure values for the controlchamber and the reference chamber from a point in time before opening ofthe valve X2 until some time after the valve X2 is opened for theembodiment of FIG. 103;

FIG. 105 is a schematic view of a control chamber of a cassette andassociated control components including pressure sensors andinflow/outflow paths in an illustrative embodiment;

FIG. 106 is a pressure versus time plot for the reference chamber andthe control chamber during a pumping and FMS process;

FIG. 107 is a flow chart of pneumatic steps of an FMS process;

FIG. 108A is a plot of the pumping chamber and reference chamberpressures during the +FMS process;

FIG. 108B is a plot of the pumping chamber and reference chamberpressures during the −FMS process;

FIG. 109A is an illustration of a polytropic conceptual model of the+FMS process involving three separate closed mass systems;

FIG. 109B is a plot of the polytropic expansion constant for +FMS versescontrol chamber volume.

FIG. 110A is an illustration of the polytropic conceptual model of the−FMS process involving three separate closed mass systems;

FIG. 110B is a plot of the polytropic expansion constant for −FMS versescontrol chamber volume.

FIG. 111 is a flow chart of basic AIA FMS calculation steps;

FIG. 112 is a more detailed flow chart of AIA FMS calculation steps;

FIG. 113A is a flow chart for an FMS calibration method for a diaphragmpump;

FIG. 113B is a flow chart for calibrating partial stroke volumes for theFMS calibration method;

FIG. 113C is a depiction of process used for calibrating partial strokevolumes in the diaphragm pump;

FIG. 113D is a depiction of correction of volume measurements duringpartial stroke calibration when the pump diaphragm approaches thechamber wall;

FIG. 114 shows a pressure tracing from a control or actuation chamber ofa pumping cassette during a liquid delivery stroke;

FIG. 115 shows a graph plotting pressure in a control or actuationchamber during a liquid deliver stroke and a cumulative volumeestimation plot during the liquid delivery stroke;

FIG. 116 shows a flowchart outlining a number of steps which may be usedto estimate control chamber volume changes over time;

FIG. 117 shows a flowchart outlining a number of steps to adjust anequation used to estimate control chamber volume changes over timeduring a pump stroke;

FIG. 118 shows a flowchart outlining a number of steps to detect end ofstroke based on flow rate during a stroke;

FIG. 119 shows a flowchart outlining a number of steps to determine endof stroke by predicting time necessary to complete a stroke;

FIG. 120 shows a flowchart outlining a number of steps to detect areduced flow condition while a pump stroke is in progress;

FIG. 121 shows a flowchart outlining a number of steps to determine atarget volume of fluid has been moved;

FIG. 122 shows a flowchart outlining steps to detect that fluid line hasbeen primed by estimating flow rate and stroke displacement;

FIG. 123 shows a flowchart outlining steps to detect that a fluid linehas been primed by estimating flow rate during pumping strokes;

FIG. 124 shows a flowchart outlining steps to detect that a fluid linehas been primed by estimating flow rate during pumping strokes;

FIG. 125 shows a flowchart outlining steps which may be used by a cyclerto differentiate which set of one or more different sets has beeninstalled in a medical device;

FIG. 126 is a perspective view of an interior section of the cycler ofFIG. 10 with the upper portion of the housing removed;

FIG. 127 is a schematic block diagram illustrating an exemplaryimplementation of control system for an APD system;

FIG. 128 shows an exemplary patient data key and associated port fortransferring patient data to and from the APD system;

FIG. 129 shows a patient data key with an alternative housingconfiguration;

FIG. 130 shows a block diagram of software subsystems of a userinterface computer and an automation computer;

FIG. 131 is a schematic block diagram illustrating an exemplaryarrangement of the multiple processors controlling the cycler and thesafe line;

FIG. 132 is a schematic block diagram illustrating exemplary connectionsbetween the hardware interface processor and the sensors, the actuatorsand the automation computer;

FIG. 133 shows a schematic cross section of the cycler illustrating thecomponents of the heater system for the heater bag;

FIG. 134 shows software processes interacting with a heater controllerprocess;

FIG. 135 shows a block diagram of a nested feedback loop to control theheater bag temperature;

FIG. 136 shows a block diagram of an alternative nested feedback loop tocontrol the heater bag temperature;

FIG. 137 shows a block diagram of another alternative nested feedbackloop to control the heater bag temperature;

FIG. 138 shows a block diagram of the thermal model of the heater bagand heater tray;

FIG. 139 shows a temperature response of the heater bag and heater trayfor nominal conditions;

FIG. 140 shows a temperature response of the heater bag and heater trayfor warm conditions;

FIG. 141 shows a temperature response of the heater bag and heater trayfor cold conditions;

FIG. 142 is a schematic block diagram of one embodiment of a heatercontrol system;

FIG. 143 is a schematic block diagram illustrating a heater circuitconfigured with a pair of heating elements;

FIG. 144 is a schematic block diagram illustrating a heater circuitconfigured with a pair of heating elements with reduced potential forcurrent leakage;

FIG. 145 is a circuit diagram of a heater circuit configured with a pairof heating elements;

FIG. 146 shows a flow chart outlining a method to select the heaterconfiguration in an APD cycler;

FIG. 147 shows a flow chart outlining a method to select the heaterconfiguration in an APD cycler where a stored value of the AC mainsvoltage is queried during selection of the heater configuration;

FIG. 148 shows an example heater circuit which may be included in anautomated dialysis machine;

FIG. 149 is a graph depicting leakage current to a heater pan from aheater element over time;

FIG. 150 is another graph depicting leakage current to a heater pan froma heater element over time;

FIG. 151 is a schematic of a heater circuit which may be included in anautomated dialysis machine;

FIG. 151A is a schematic of a heater circuit with a safety voltagesource;

FIG. 152 depicts an AC mains input for the example circuit of FIG. 148;

FIG. 153 depicts AC mains input connected to the AC switch of thecircuit of FIG. 148;

FIG. 154 shows first and second lines of AC mains switch outs connectedto pulse width modulated elements;

FIG. 155 depicts a modulation or gating circuit that may be used in thecircuit of FIGS. 148-154;

FIG. 156 depicts a modulation or gating circuit similar to that of FIG.155;

FIG. 157 depicts example circuitry that may be included in a heatercircuit that includes a current sense element;

FIG. 158 shows a flow of information between various subsystems andprocesses of the APD system;

FIG. 159 illustrates an operation of the therapy subsystem of FIG. 157;

FIG. 160 is a sequence diagram depicting interactions of therapy moduleprocesses during initial replenish and dialyze portions of the therapy;

FIGS. 161-166 show screen views relating to alerts and alarms that maybe displayed on a touch screen user interface for the APD system;

FIG. 167 illustrates component states and operations for error conditiondetection and recovery;

FIG. 168 shows exemplary modules of a UI view subsystem for the APDsystem;

FIG. 169 shows an illustrative user interface initial screen thatprovides the user the option of selecting between start therapy orsettings;

FIG. 170 shows an illustrative user interface status screen thatprovides information on the status of the therapy;

FIG. 171 shows an illustrative user interface menu screen with variouscomfort settings;

FIG. 172 shows an illustrative user interface help menu screen;

FIG. 173 shows an illustrative user interface screen that allows a userto set a set of parameters;

FIG. 174 shows an illustrative user interface screen that allows a userto adjust the minimum drain volume;

FIG. 175 shows an illustrative user interface screen that allows a userto review and confirm the settings;

FIG. 176 is an illustration of an adaptive tidal therapy mode duringCCPD;

FIG. 177 is an illustration of the implementation of a revised-cyclemode during CCPD;

FIG. 178 is an illustration of the implementation of a revised-cyclemode during a tidal therapy;

FIG. 179 is an illustration of the implementation of an adaptive tidalmode during a tidal therapy;

FIG. 180 is an illustration showing peritoneal volume over time for atidal therapy;

FIG. 181 is another illustration showing peritoneal volume over time fora tidal therapy;

FIG. 182 is an illustration of peritoneal volume over time for a tidaltherapy which includes an adapted fill;

FIG. 183 shows a flow chart depicting an embodiment of synchronizationof operations between two pumping chambers of a pump cassette;

FIG. 184 shows a flow chart depicting another embodiment ofsynchronization of operations between two pumping chambers of a pumpcassette;

FIG. 185 shows a flow chart depicting another embodiment ofsynchronization of operations between two pumping chambers of a pumpcassette;

FIG. 186 shows a flow chart depicting another embodiment ofsynchronization of operations between two pumping chambers of a pumpcassette, including venting;

FIG. 187A shows a flow chart depicting another embodiment ofsynchronization of operations between two pumping chambers of a pumpcassette, including venting;

FIG. 187B depicts an example graph that plots pressure in a controlchamber over a deliver stroke, back pressure relief step, and volumemeasurement step;

FIG. 188 shows a flow chart depicting another embodiment ofsynchronization of operations between two pumping chambers of a pumpcassette, including venting;

FIG. 189 shows a flow chart depicting another embodiment ofsynchronization of operations between two pumping chambers of a pumpcassette, including venting;

FIG. 190 shows a flowchart depicting a synchronization scheme in whichpump chambers are treated as independent state machines which acquireexclusive access tokens;

FIG. 191 shows a flowchart in which the amount of fluid moved during apumping stroke is checked before that chamber releases possession of atoken;

FIG. 192 shows a flowchart outlining steps which may be used when a pumpchamber is performing an FMS measurement;

FIG. 193 shows a flowchart outlining steps which may be used when a pumpchamber is performing an FMS measurement synchronized using an FMStoken;

FIG. 194 shows a relationship between pressure tracings of a two-pumpapparatus and resource tokens assigned to the pumps at various timesduring pumping operations;

FIG. 195 shows a relationship between pressure tracings of a two-pumpapparatus and resource tokens assigned to the pumps during initiation ofa pumping operation;

FIG. 196 shows a relationship between pressure tracings of a two-pumpapparatus and resource tokens assigned to the pumps during a pumpchamber fill transition between the two pumps;

FIG. 197 shows a relationship between pressure tracings of a two-pumpapparatus and resource tokens assigned to the pumps when the pumps arestopped;

FIG. 198 depicts is a graph showing pressures of a pair of pump chambersand assignment of resource tokens during a number of pump strokes andchamber volume measurements;

FIG. 199 is a graph showing pressures (in kPa) of pumping chambers aswell as the ownership status of a number of resources and tokens over anumber of pump strokes;

FIG. 200 shows a device housing portion with a molded-in pressurereservoir;

FIG. 201 shows the device housing portion of FIG. 200, with a sealingmember covering the pressure reservoir;

FIG. 202 shows a device housing portion with another embodiment of amolded-in pressure reservoir having two compartments;

FIG. 203 shows the device housing portion of FIG. 202, with a sealingmember covering the pressure reservoir;

FIG. 204 is a bottom plan view of the housing portion of FIG. 202;

FIG. 205 is a perspective view of internal features of a device housingportion;

FIG. 206 shows a sealing member with reinforcing ribs;

FIG. 207 shows another embodiment of a two-compartment pressurereservoir assembly suitable for co-molding with or attachment to adevice housing portion;

FIG. 208 is a bottom plan view of the assembly of FIG. 207;

FIG. 209 is a view of the assembly of FIG. 207 as seen from within ahousing portion into which the assembly is included;

FIG. 210 is a cross-sectional view of the assembly of FIG. 207 at alocation indicated by FIG. 209;

FIG. 211 shows a flowchart outlining steps which may be used toreplenish a heater bag with dialysate solution;

FIG. 212 shows a flowchart outlining steps which may be employed by acycler which uses solution expiration timers;

FIG. 213 shows an example screen which may be generated by a processorfor display on a user interface of a cycler indicating a solutionexpiration timer;

FIG. 214A and FIG. 214B are flowcharts of a cycler performing an initialdrain that starts with a flow check;

FIG. 215 shows a screen shot which may be generated for display on auser interface of a cycler during a drain that includes a soft drainoption;

FIG. 216 shows a flowchart outlining steps which may be used to programand collected an automated effluent sample using a cycler; and

FIG. 217 shows a flowchart outlining steps which may be used to programand collected an automated effluent sample using a cycler.

DETAILED DESCRIPTION

Although aspects of the invention are described in relation to aperitoneal dialysis system, certain aspects of the invention can be usedin other medical applications, including infusion systems such asintravenous infusion systems or extracorporeal blood flow systems, andirrigation and/or fluid exchange systems for the stomach, intestinaltract, urinary bladder, pleural space or other body or organ cavity.Thus, aspects of the invention are not limited to use in peritonealdialysis in particular, or dialysis in general.

APD System

FIG. 1 shows an automated peritoneal dialysis (APD) system 10 that mayincorporate one or more aspects of the invention. As shown in FIG. 1,for example, the system 10 in this illustrative embodiment includes adialysate delivery set 12 (which, in certain embodiments, can be adisposable set), a cycler 14 that interacts with the delivery set 12 topump liquid provided by a solution container 20 (e.g., a bag), and acontrol system 16 (e.g., including a programmed computer or other dataprocessor, computer memory, an interface to provide information to andreceive input from a user or other device, one or more sensors,actuators, relays, pneumatic pumps, tanks, a power supply, and/or othersuitable components—only a few buttons for receiving user control inputare shown in FIG. 1, but further details regarding the control systemcomponents are provided below) that governs the process to perform anAPD procedure. In this illustrative embodiment, the cycler 14 and thecontrol system 16 are associated with a common housing 82, but may beassociated with two or more housings and/or may be separate from eachother. The cycler 14 may have a compact footprint, suited for operationupon a table top or other relatively small surface normally found in thehome. The cycler 14 may be lightweight and portable, e.g., carried byhand via handles at opposite sides of the housing 82.

The set 12 in this embodiment is intended to be a single use, disposableitem, but instead may have one or more reusable components, or may bereusable in its entirety. The user associates the set 12 with the cycler14 before beginning each APD therapy session, e.g., by mounting acassette 24 within a front door 141 of the cycler 14, which interactswith the cassette 24 to pump and control fluid flow in the various linesof the set 12. For example, dialysate may be pumped both to and from thepatient to effect APD. Post therapy, the user may remove all or part ofthe components of the set 12 from the cycler 14.

As is known in the art, prior to use, the user may connect a patientline 34 of the set 12 to his/her indwelling peritoneal catheter (notshown) at a connection 36. In one embodiment, the cycler 14 may beconfigured to operate with one or more different types of cassettes 24,such as those having differently sized patient lines 34. For example,the cycler 14 may be arranged to operate with a first type of cassettewith a patient line 34 sized for use with an adult patient, and a secondtype of cassette with a patient line 34 sized for an infant or pediatricuse. The pediatric patient line 34 may be shorter and have a smallerinner diameter than the adult line so as to minimize the volume of theline, allowing for more controlled delivery of dialysate and helping toavoid returning a relatively large volume of used dialysate to thepediatric patient when the set 12 is used for consecutive drain and fillcycles. A heater bag 22, which is connected to the cassette 24 by a line26, may be placed on a heater container receiving portion (in this case,a tray) 142 of the cycler 14. The cycler 14 may pump fresh dialysate(via the cassette 24) into the heater bag 22 so that the dialysate maybe heated by the heater tray 142, e.g., by electric resistance heatingelements associated with the tray 142 to a temperature of about 37degrees C. Heated dialysate may be provided from the heater bag 22 tothe patient via the cassette 24 and the patient line 34. In analternative embodiment, the dialysate can be heated on its way to thepatient as it enters, or after it exits, the cassette 24 by passing thedialysate through tubing in contact with the heater tray 142, or throughan in-line fluid heater (which may be provided in the cassette 24). Useddialysate may be pumped from the patient via the patient line 34 to thecassette 24 and into a drain line 28, which may include one or moreclamps to control flow through one or more branches of the drain line28. In this illustrative embodiment, the drain line 28 may include aconnector 39 for connecting the drain line 28 to a dedicated drainreceptacle, and an effluent sample port 282 for taking a sample of useddialysate for testing or other analysis. The user may also mount thelines 30 of one or more containers 20 within the door 141. The lines 30may also be connected to a continuous or real-time dialysate preparationsystem. (The lines 26, 28, 30, 34 may include a flexible tubing and/orsuitable connectors and other components (such as pinch valves, etc.) asdesired.) The containers 20 may contain sterile peritoneal dialysissolution for infusion, or other materials (e.g., materials used by thecycler 14 to formulate dialysate by mixing with water, or admixingdifferent types of dialysate solutions). The lines 30 may be connectedto spikes 160 of the cassette 24, which are shown in FIG. 1 covered byremovable caps. In one aspect of the invention described in more detailbelow, the cycler 14 may automatically remove caps from one or morespikes 160 of the cassette 24 and connect lines 30 of solutioncontainers 20 to respective spikes 160. This feature may help reduce thepossibility of infection or contamination by reducing the chance ofcontact of non-sterile items with the spikes 160.

In another aspect, a dialysate delivery set 12 a may not have cassettespikes 160. Instead, one or more solution lines 30 may be permanentlyaffixed to the inlet ports of cassette 24, as shown in FIG. 1A. In thiscase, each solution line 30 may have a (capped) spike connector 35 formanual connection to a solution container or dialysate bag 20.

With various connections made, the control system 16 may pace the cycler14 through a series of fill, dwell, and/or drain cycles typical of anAPD procedure. For example, during a fill phase, the cycler 14 may pumpdialysate (by way of the cassette 24) from one or more containers 20 (orother source of dialysate supply) into the heater bag 22 for heating.Thereafter, the cycler 14 may infuse heated dialysate from the heaterbag 22 through the cassette 24 and into the patient's peritoneal cavityvia the patient line 34. Following a dwell phase, the cycler 14 mayinstitute a drain phase, during which the cycler 14 pumps used dialysatefrom the patient via the line 34 (again by way of the cassette 24), anddischarges spent dialysis solution into a nearby drain (not shown) viathe drain line 28.

The cycler 14 does not necessarily require the solution containers 20and/or the heater bag 22 to be positioned at a prescribed head heightabove the cycler 14, e.g., because the cycler 14 is not necessarily agravity flow system. Instead, the cycler 14 may emulate gravity flow, orotherwise suitably control flow of dialysate solution, even with thesource solution containers 20 above, below or at a same height as thecycler 14, with the patient above or below the cycler, etc. For example,the cycler 14 can emulate a fixed head height during a given procedure,or the cycler 14 can change the effective head height to either increaseor decrease pressure applied to the dialysate during a procedure. Thecycler 14 may also adjust the rate of flow of dialysate. In one aspectof the invention, the cycler 14 may adjust the pressure and/or flow rateof dialysate when provided to the patient or drawn from the patient soas to reduce the patient's sensation of the fill or drain operation.Such adjustment may occur during a single fill and/or drain cycle, ormay be adjusted across different fill and/or drain cycles. In oneembodiment, the cycler 14 may taper the pressure used to draw useddialysate from the patient near the end of a drain operation. Becausethe cycler 14 may establish an artificial head height, it may have theflexibility to interact with and adapt to the particular physiology orchanges in the relative elevation of the patient.

Cassette

In one aspect of the invention, a cassette 24 may include patient anddrain lines that are separately occludable with respect to solutionsupply lines. That is, safety critical flow to and from patient line maybe controlled, e.g., by pinching the lines to stop flow, without theneed to occlude flow through one or more solution supply lines. Thisfeature may allow for a simplified occluder device since occlusion maybe performed with respect to only two lines as opposed to occludingother lines that have little or no effect on patient safety. Forexample, in a circumstance where a patient or drain connection becomesdisconnected, the patient and drain lines may be occluded. However, thesolution supply and/or heater bag lines may remain open for flow,allowing the cycler 14 to prepare for a next dialysis cycle; e.g.,separate occlusion of patient and drain lines may help ensure patientsafety while permitting the cycler 14 to continue to pump dialysate fromone or more containers 20 to the heater bag 22 or to other solutioncontainers 20.

In another aspect of the invention, the cassette may have patient, drainand heater bag lines at one side or portion of the cassette and one ormore solution supply lines at another side or portion of the cassette,e.g., an opposite side of the cassette. Such an arrangement may allowfor separate occlusion of patient, drain or heater bag lines withrespect to solution lines as discussed above. Physically separating thelines attached to the cassette by type or function allows for moreefficient control of interaction with lines of a certain type orfunction. For example, such an arrangement may allow for a simplifiedoccluder design because less force is required to occlude one, two orthree of these lines than all lines leading to or away from thecassette. Alternately, this arrangement may allow for more effectiveautomated connection of solution supply lines to the cassette, asdiscussed in more detail below. That is, with solution supply lines andtheir respective connections located apart from patient, drain and/orheater bag lines, an automated de-capping and connection device mayremove caps from spikes on the cassette as well as caps on solutionsupply lines, and connect the lines to respective spikes withoutinterference by the patient, drain or heater bag lines.

FIG. 2 shows an illustrative embodiment of a cassette 24 thatincorporates aspects of the invention described above. In thisembodiment, the cassette 24 has a generally planar body and the heaterbag line 26, the drain line 28 and the patient line 34 are connected atrespective ports on the left end of the cassette body, while the rightend of the cassette body may include five spikes 160 to which solutionsupply lines 30 may be connected. In the arrangement shown in FIG. 2,each of the spikes 160 is covered by a spike cap 63, which may beremoved, exposing the respective spike and allowing connection to arespective line 30. As described above, the lines 30 may be attached toone or more solution containers or other sources of material, e.g., foruse in dialysis and/or the formulation of dialysate, or connected to oneor more collection bags for sampling purposes or for peritonealequilibration testing (PET test).

FIGS. 3 and 4 show exploded views (perspective and top views,respectively) of the cassette 24 in this illustrative embodiment. Thecassette 24 is formed as a relatively thin and flat member having agenerally planar shape, e.g., may include components that are molded,extruded or otherwise formed from a suitable plastic. In thisembodiment, the cassette 24 includes a base member 18 that functions asa frame or structural member for the cassette 24 as well as forming, atleast in part, various flow channels, ports, valve portions, etc. Thebase member 18 may be molded or otherwise formed from a suitable plasticor other material, such as a polymethyl methacrylate (PMMA) acrylic, ora cyclic olefin copolymer/ultra low density polyethylene (COC/ULDPE),and may be relatively rigid. In an embodiment, the ratio of COC to ULDPEcan be approximately 85%/15%. FIG. 3 also shows the ports for the heaterbag (port 150), drain (port 152) and the patient (port 154) that areformed in the base member 18. Each of these ports may be arranged in anysuitable way, such as, for example, a central tube 156 extending from anouter ring or skirt 158, or a central tube alone. Flexible tubing foreach of the heater bag, drain and patient lines 26, 28, 34 may beconnected to the central tube 156 and engaged by the outer ring 158, ifpresent.

Both sides of the base member 18 may be covered, at least in part, by amembrane 15 and 16, e.g., a flexible polymer film made from, forexample, polyvinyl chloride (PVC), that is cast, extruded or otherwiseformed. Alternatively, the sheet may be formed as a laminate of two ormore layers of poly-cyclohexylene dimethylene cyclohexanedicarboxylate(PCCE) and/or ULDPE, held together, for example, by a coextrudableadhesive (CXA). In some embodiments, the membrane thickness may be inthe range of approximately 0.002 to 0.020 inches thick. In a preferredembodiment, the thickness of a PVC-based membrane may be in the range ofapproximately 0.012 to 0.016 inches thick, and more preferablyapproximately 0.014 inches thick. In another preferred embodiment, suchas, for example, for laminate sheets, the thickness of the laminate maybe in the range of approximately 0.006 to 0.010 inches thick, and morepreferably approximately 0.008 inches thick.

Both membranes 15 and 16 may function not only to close or otherwiseform a part of flowpaths of the cassette 24, but also may be moved orotherwise manipulated to open/close valve ports and/or to function aspart of a pump diaphragm, septum or wall that moves fluid in thecassette 24. For example, the membranes 15 and 16 may be positioned onthe base member 18 and sealed (e.g., by heat, adhesive, ultrasonicwelding or other means) to a rim around the periphery of the base member18 to prevent fluid from leaking from the cassette 24. The membrane 15may also be bonded to other, inner walls of the base member 18, e.g.,those that form various channels, or may be pressed into sealing contactwith the walls and other features of the base member 18 when thecassette 24 suitably mounted in the cycler 14. Thus, both of themembranes 15 and 16 may be sealed to a peripheral rim of the base member18, e.g., to help prevent leaking of fluid from the cassette 24 upon itsremoval from the cycler 14 after use, yet be arranged to lie,unattached, over other portions of the base member 18. Once placed inthe cycler 14, the cassette 24 may be squeezed between opposed gasketsor other members so that the membranes 15 and 16 are pressed intosealing contact with the base member 18 at regions inside of theperiphery, thereby suitably sealing channels, valve ports, etc., fromeach other.

Other arrangements for the membranes 15 and 16 are possible. Forexample, the membrane 16 may be formed by a rigid sheet of material thatis bonded or otherwise made integral with the body 18. Thus, themembrane 16 need not necessarily be, or include, a flexible member.Similarly, the membrane 15 need not be flexible over its entire surface,but instead may include one or more flexible portions to permit pumpand/or valve operation, and one or more rigid portions, e.g., to closeflowpaths of the cassette 24. It is also possible that the cassette 24may not include the membrane 16 or the membrane 15, e.g., where thecycler 14 includes a suitable member to seal pathways of the cassette,control valve and pump function, etc.

In accordance with another aspect of the invention, the membrane 15 mayinclude a pump chamber portion 151 (“pump membrane”) that is formed tohave a shape that closely conforms to the shape of a corresponding pumpchamber 181 depression in the base 18. For example, the membrane 15 maybe generally formed as a flat member with thermoformed (or otherwiseformed) dome-like shapes 151 that conform to the pump chamberdepressions of the base member 18. The dome-like shape of the pre-formedpump chamber portions 151 may be constructed, for example, by heatingand forming the membrane over a vacuum form mold of the type shown inFIG. 5. As shown in FIG. 5, the vacuum may be applied through acollection of holes along the wall of the mold. Alternatively, the wallof the mold can be constructed of a porous gas-permeable material, whichmay result in a more uniformly smooth surface of the molded membrane. Inone example, the molded membrane sheet 15 is trimmed while attached tothe vacuum form mold. The vacuum form mold then presses the trimmedmembrane sheet 15 against the cassette body 18 and bonds them together.In one embodiment the membrane sheets 15,16 are heat-welded to thecassette body 18. In this way, the membrane 15 may move relative to thepump chambers 181 to effect pumping action without requiring stretchingof the membrane 15 (or at least minimal stretching of the membrane 15),both when the membrane 15 is moved maximally into the pump chambers 181and (potentially) into contact with spacer elements 50 (e.g., as shownin solid line in FIG. 4 while pumping fluid out of the pump chamber181), and when the membrane 15 is maximally withdrawn from the pumpchamber 181 (e.g., as shown in dashed line in FIG. 4 when drawing fluidinto the pump chamber 181). Avoiding stretching of the membrane 15 mayhelp prevent pressure surges or other changes in fluid delivery pressuredue to sheet stretch and/or help simplify control of the pump whenseeking to minimize pressure variation during pump operation. Otherbenefits may be found, including reduced likelihood of membrane 15failure (e.g., due to tears in the membrane 15 resulting from stressesplace on the membrane 15 during stretching), and/or improved accuracy inpump delivery volume measurement, as described in more detail below. Inone embodiment, the pump chamber portions 151 may be formed to have asize (e.g., a define a volume) that is about 85-110% of the pump chamber181, e.g., if the pump chamber portions 151 define a volume that isabout 100% of the pump chamber volume, the pump chamber portion 151 maylie in the pump chamber 181 and in contact with the spacers 50 while atrest and without being stressed.

Providing greater control of the pressure used to generate a fill anddelivery stroke of liquid into and out of a pump chamber may haveseveral advantages. For example, it may be desirable to apply theminimum negative pressure possible when the pump chamber draws fluidfrom the patient's peritoneal cavity during a drain cycle. A patient mayexperience discomfort during the drain cycle of a treatment in partbecause of the negative pressure being applied by the pumps during afill stroke. The added control that a pre-formed membrane can provide tothe negative pressure being applied during a fill stroke may help toreduce the patient's discomfort.

A number of other benefits may be realized by using pump membranespre-formed to the contour of the cassette pump chamber. For example, theflow rate of liquid through the pump chamber can be made more uniform,because a constant pressure or vacuum can be applied throughout the pumpstroke, which in turn may simplify the process of regulating the heatingof the liquid. Moreover, temperature changes in the cassette pump mayhave a smaller effect on the dynamics of displacing the membrane, aswell as the accuracy of measuring pressures within the pump chambers. Inaddition, pressure spikes within the fluid lines can be minimized. Also,correlating the pressures measured by pressure transducers on thecontrol (e.g. pneumatic) side of the membrane with the actual pressureof the liquid on the pump chamber side of the membrane may be simpler.This in turn may permit more accurate head height measurements of thepatient and fluid source bags prior to therapy, improve the sensitivityof detecting air in the pump chamber, and improve the accuracy ofvolumetric measurements. Furthermore, eliminating the need to stretchthe membrane may allow for the construction and use of pump chambershaving greater volumes.

In this embodiment, the cassette 24 includes a pair of pump chambers 181that are formed in the base member 18, although one pump chamber or morethan two pump chambers are possible. In accordance with an aspect of theinvention, the inner wall of pump chambers 181 includes spacer elements50 that are spaced from each other and extend from the inner wall ofpump chamber 18 to help prevent portions of the membrane 15 fromcontacting the inner wall of pump chamber 181. (As shown on theright-side pump chamber 181 in FIG. 4, the inner wall is defined by sideportions 181 a and a bottom portion 181 b. The spacers 50 extendupwardly from the bottom portion 181 b in this embodiment, but couldextend from the side portions 181 a or be formed in other ways.) Bypreventing contact of the membrane 15 with the pump chamber inner wall,the spacer elements 50 may provide a dead space (or trap volume) whichmay help trap air or other gas in the pump chamber 181 and inhibit thegas from being pumped out of the pump chamber 181 in some circumstances.In other cases, the spacers 50 may help the gas move to an outlet of thepump chamber 181 so that the gas may be removed from the pump chamber181, e.g., during priming. Also, the spacers 50 may help prevent themembrane 15 from sticking to the pump chamber inner wall and/or allowflow to continue through the pump chamber 181, even if the membrane 15is pressed into contact with the spacer elements 50. In addition, thespacers 50 help to prevent premature closure of the outlet port of thepump chamber (openings 187 and/or 191) if the sheet happens to contactthe pump chamber inner wall in a non-uniform manner. Further detailsregarding the arrangement and/or function of spacers 50 are provided inU.S. Pat. Nos. 6,302,653 and 6,382,923, both of which are incorporatedherein by reference.

In this embodiment, the spacer elements 50 are arranged in a kind of“stadium seating” arrangement such that the spacer elements 50 arearranged in a concentric elliptical pattern with ends of the spacerelements 50 increasing in height from the bottom portion 181 b of theinner wall with distance away from the center of the pump chamber 181 toform a semi-elliptical domed shaped region (shown by dotted line in FIG.4). Positioning spacer elements 50 such that the ends of the spacerelements 50 form a semi-elliptical region that defines the domed regionintended to be swept by the pump chamber portion 151 of the membrane 15may allow for a desired volume of dead space that minimizes anyreduction to the intended stroke capacity of pump chambers 181. As canbe seen in FIG. 3 (and FIG. 6), the “stadium seating” arrangement inwhich spacer elements 50 are arranged may include “aisles” or breaks 50a in the elliptical pattern. Breaks (or aisles) 50 a help to maintain anequal gas level throughout the rows (voids or dead space) 50 b betweenspacer elements 50 as fluid is delivered from the pump chamber 181. Forexample, if the spacer elements 50 were arranged in the stadium seatingarrangement shown in FIG. 6 without breaks (or aisles) 50 a or othermeans of allowing liquid and air to flow between spacer elements 50, themembrane 15 might bottom out on the spacer element 50 located at theoutermost periphery of the pump chamber 181, trapping whatever gas orliquid is present in the void between this outermost spacer element 50and the side portions 181 a of the pump chamber wall. Similarly, if themembrane 15 bottomed out on any two adjacent spacer elements 50, any gasand liquid in the void between the elements 50 may become trapped. Insuch an arrangement, at the end of the pump stroke, air or other gas atthe center of pump chamber 181 could be delivered while liquid remainsin the outer rows. Supplying breaks (or aisles) 50 a or other means offluidic communication between the voids between spacer elements 50 helpsto maintain an equal gas level throughout the voids during the pumpstroke, such that air or other gas may be inhibited from leaving thepump chamber 181 unless the liquid volume has been substantiallydelivered.

In certain embodiments, spacer elements 50 and/or the membrane 15 may bearranged so that the membrane 15 generally does not wrap or otherwisedeform around individual spacers 50 when pressed into contact with them,or otherwise extend significantly into the voids between spacers 50.Such an arrangement may lessen any stretching or damage to membrane 15caused by wrapping or otherwise deforming around one or more individualspacer elements 50. For example, it has also been found to beadvantageous in this embodiment to make the size of the voids betweenspacers 50 approximately equal in width to the width of the spacers 50.This feature has shown to help prevent deformation of the membrane 15,e.g., sagging of the membrane into the voids between spacers 50, whenthe membrane 15 is forced into contact with the spacers 50 during apumping operation.

In accordance with another aspect of the invention, the inner wall ofpump chambers 181 may define a depression that is larger than the space,for example a semi-elliptical or domed space, intended to be swept bythe pump chamber portion 151 of the membrane 15. In such instances, oneor more spacer elements 50 may be positioned below the domed regionintended to be swept by the membrane portion 151 rather than extendinginto that domed region. In certain instances, the ends of spacerelements 50 may define the periphery of the domed region intended to beswept by the membrane 15. Positioning spacer elements 50 outside of, oradjacent to, the periphery of the domed region intended to be swept bythe membrane portion 151 may have a number of advantages. For example,positioning one or more spacer elements 50 such that the spacer elementsare outside of, or adjacent to, the domed region intended to be swept bythe flexible membrane provides a dead space between the spacers and themembrane, such as described above, while minimizing any reduction to theintended stroke capacity of pump chambers 181.

It should be understood that the spacer elements 50, if present, in apump chamber may be arranged in any other suitable way, such as forexample, shown in FIG. 7. The left side pump chamber 181 in FIG. 7includes spacers 50 arranged similarly to that in FIG. 6, but there isonly one break or aisle 50 a that runs vertically through theapproximate center of the pump chamber 181. The spacers 50 may bearranged to define a concave shape similar to that in FIG. 6 (i.e., thetops of the spacers 50 may form the semi-elliptical shape shown in FIGS.3 and 4), or may be arranged in other suitable ways, such as to form aspherical shape, a box-like shape, and so on. The right-side pumpchamber 181 in FIG. 7 shows an embodiment in which the spacers 50 arearranged vertically with voids 50 b between spacers 50 also arrangedvertically. As with the left-side pump chamber, the spacers 50 in theright-side pump chamber 181 may define a semi-elliptical, spherical,box-like or any other suitably shaped depression. It should beunderstood, however, that the spacer elements 50 may have a fixedheight, a different spatial pattern than those shown, and so on.

Also, the membrane 15 may itself have spacer elements or other features,such as ribs, bumps, tabs, grooves, channels, etc., in addition to, orin place of the spacer elements 50. Such features on the membrane 15 mayhelp prevent sticking of the membrane 15, etc., and/or provide otherfeatures, such as helping to control how the sheet folds or otherwisedeforms when moving during pumping action. For example, bumps or otherfeatures on the membrane 15 may help the sheet to deform consistentlyand avoid folding at the same area(s) during repeated cycles. Folding ofa same area of the membrane 15 at repeated cycles may cause the membrane15 to prematurely fail at the fold area, and thus features on themembrane 15 may help control the way in which folds occur and where.

In this illustrative embodiment, the base member 18 of the cassette 24defines a plurality of controllable valve features, fluid pathways andother structures to guide the movement of fluid in the cassette 24. FIG.6 shows a plan view of the pump chamber side of the base member 18,which is also seen in perspective view in FIG. 3. FIG. 8 shows aperspective view of a back side of the base member 18, and FIG. 9 showsa plan view of the back side of the base member 18. The tube 156 foreach of the ports 150, 152 and 154 fluidly communicates with arespective valve well 183 that is formed in the base member 18. Thevalve wells 183 are fluidly isolated from each other by wallssurrounding each valve well 183 and by sealing engagement of themembrane 15 with the walls around the wells 183. As mentioned above, themembrane 15 may sealingly engage the walls around each valve well 183(and other walls of the base member 18) by being pressed into contactwith the walls, e.g., when loaded into the cycler 14. Fluid in the valvewells 183 may flow into a respective valve port 184, if the membrane 15is not pressed into sealing engagement with the valve port 184. Thus,each valve port 184 defines a valve (e.g., a “volcano valve”) that canbe opened and closed by selectively moving a portion of the membrane 15associated with the valve port 184. As will be described in more detailbelow, the cycler 14 may selectively control the position of portions ofthe membrane 15 so that valve ports (such as ports 184) may be opened orclosed so as to control flow through the various fluid channels andother pathways in the cassette 24. Flow through the valve ports 184leads to the back side of the base member 18. For the valve ports 184associated with the heater bag and the drain (ports 150 and 152), thevalve ports 184 lead to a common channel 200 formed at the back side ofthe base member 18. As with the valve wells 183, the channel 200 isisolated from other channels and pathways of the cassette 24 by thesheet 16 making sealing contact with the walls of the base member 18that form the channel 200. For the valve port 184 associated with thepatient line port 154, flow through the port 184 leads to a commonchannel 202 on the back side of the base member 18. Common channel 200may also be referred to herein as an upper fluidic bus and commonchannel 202 may also be referred to herein as a lower fluidic bus.

Returning to FIG. 6, each of the spikes 160 (shown uncapped in FIG. 6)fluidly communicates with a respective valve well 185, which areisolated from each other by walls and sealing engagement of the membrane15 with the walls that form the wells 185. Fluid in the valve wells 185may flow into a respective valve port 186, if the membrane 15 is not insealing engagement with the port 186. (Again, the position of portionsof the membrane 15 over each valve port 186 can be controlled by thecycler 14 to open and close the valve ports 186.) Flow through the valveports 186 leads to the back side of the base member 18 and into thecommon channel 202. Thus, in accordance with one aspect of theinvention, a cassette may have a plurality of solution supply lines (orother lines that provide materials for providing dialysate) that areconnected to a common manifold or channel of the cassette, and each linemay have a corresponding valve to control flow from/to the line withrespect to the common manifold or channel. Fluid in the channel 202 mayflow into lower openings 187 of the pump chambers 181 by way of openings188 that lead to lower pump valve wells 189 (see FIG. 6). Flow from thelower pump valve wells 189 may pass through a respective lower pumpvalve port 190 if a respective portion of the membrane 15 is not pressedin sealing engagement with the port 190. As can be seen in FIG. 9, thelower pump valve ports 190 lead to a channel that communicates with thelower openings 187 of the pump chambers 181. Flow out of the pumpchambers 181 may pass through the upper openings 191 and into a channelthat communicates with an upper valve port 192. Flow from the uppervalve port 192 (if the membrane 15 is not in sealing engagement with theport 192) may pass into a respective upper valve well 194 and into anopening 193 that communicates with the common channel 200 on the backside of the base member 18.

As will be appreciated, the cassette 24 may be controlled so that thepump chambers 181 can pump fluid from and/or into any of the ports 150,152 and 154 and/or any of the spikes 160. For example, fresh dialysateprovided by one of the containers 20 that is connected by a line 30 toone of the spikes 160 may be drawn into the common channel 202 byopening the appropriate valve port 186 for the proper spike 160 (andpossibly closing other valve ports 186 for other spikes). Also, thelower pump valve ports 190 may be opened and the upper pump valve ports192 may be closed. Thereafter, the portion of the membrane 15 associatedwith the pump chambers 181 (i.e., pump membranes 151) may be moved(e.g., away from the base member 18 and the pump chamber inner wall) soas to lower the pressure in the pump chambers 181, thereby drawing fluidin through the selected spike 160 through the corresponding valve port186, into the common channel 202, through the openings 188 and into thelower pump valve wells 189, through the (open) lower pump valve ports190 and into the pump chambers 181 through the lower openings 187. Thevalve ports 186 are independently operable, allowing for the option todraw fluid through any one or a combination of spikes 160 and associatedsource containers 20, in any desired sequence, or simultaneously. (Ofcourse, only one pump chamber 181 need be operable to draw fluid intoitself. The other pump chamber may be left inoperable and closed off toflow by closing the appropriate lower pump valve port 190.)

With fluid in the pump chambers 181, the lower pump valve ports 190 maybe closed, and the upper pump valve ports 192 opened. When the membrane15 is moved toward the base member 18, the pressure in the pump chambers181 may rise, causing fluid in the pump chambers 181 to pass through theupper openings 191, through the (open) upper pump valve ports 192 andinto the upper pump valve wells 194, through the openings 193 and intothe common channel 200. Fluid in the channel 200 may be routed to theheater bag port 150 and/or the drain port 152 (and into thecorresponding heater bag line or drain line) by opening the appropriatevalve port 184. In this way, for example, fluid in one or more of thecontainers 20 may be drawn into the cassette 24, and pumped out to theheater bag 22 and/or the drain.

Fluid in the heater bag 22 (e.g., after having been suitably heated onthe heater tray for introduction into the patient) may be drawn into thecassette 24 by opening the valve port 184 for the heater bag port 150,closing the lower pump valve ports 190, and opening the upper pump valveports 192. By moving the portions of the membrane 15 associated with thepump chambers 181 away from the base member 18, the pressure in the pumpchambers 181 may be lowered, causing fluid flow from the heater bag 22and into the pump chambers 181. With the pump chambers 181 filled withheated fluid from the heater bag 22, the upper pump valve ports 192 maybe closed and the lower pump valve ports 190 opened. To route the heateddialysate to the patient, the valve port 184 for the patient port 154may be opened and valve ports 186 for the spikes 160 closed. Movement ofthe membrane 15 in the pump chambers 181 toward the base member 18 mayraise the pressure in the pump chambers 181 causing fluid to flowthrough the lower pump valve ports 190, through the openings 188 andinto the common channel 202 to, and through, the (open) valve port 184for the patient port 154. This operation may be repeated a suitablenumber of times to transfer a desired volume of heated dialysate to thepatient.

When draining the patient, the valve port 184 for the patient port 154may be opened, the upper pump valve ports 192 closed, and the lower pumpvalve ports 190 opened (with the spike valve ports 186 closed). Themembrane 15 may be moved to draw fluid from the patient port 154 andinto the pump chambers 181. Thereafter, the lower pump valve ports 190may be closed, the upper valve ports 192 opened, and the valve port 184for the drain port 152 opened. Fluid from the pump chambers 181 may thenbe pumped into the drain line for disposal or for sampling into a drainor collection container. (Alternatively, fluid may also be routed to oneor more spikes 160/lines 30 for sampling or drain purposes). Thisoperation may be repeated until sufficient dialysate is removed from thepatient and pumped to the drain.

The heater bag 22 may also serve as a mixing container. Depending on thespecific treatment requirements for an individual patient, dialysate orother solutions having different compositions can be connected to thecassette 24 via suitable solution lines 30 and spikes 160. Measuredquantities of each solution can be added to heater bag 22 using cassette24, and admixed according to one or more pre-determined formulae storedin microprocessor memory and accessible by control system 16.Alternatively, specific treatment parameters can be entered by the uservia user interface 144. The control system 16 can be programmed tocompute the proper admixture requirements based on the type of dialysateor solution containers connected to spikes 160, and can then control theadmixture and delivery of the prescribed mixture to the patient.

In accordance with an aspect of the invention, the pressure applied bythe pumps to dialysate that is infused into the patient or removed fromthe patient may be controlled so that patient sensations of “tugging” or“pulling” resulting from pressure variations during drain and filloperations may be minimized. For example, when draining dialysate, thesuction pressure (or vacuum/negative pressure) may be reduced near theend of the drain process, thereby minimizing patient sensation ofdialysate removal. A similar approach may be used when nearing the endof a fill operation, i.e., the delivery pressure (or positive pressure)may be reduced near the end of fill. Different pressure profiles may beused for different fill and/or drain cycles in case the patient is foundto be more or less sensitive to fluid movement during different cyclesof the therapy. For example, a relatively higher (or lower) pressure maybe used during fill and/or drain cycles when a patient is asleep, ascompared to when the patient is awake. The cycler 14 may detect thepatient's sleep/awake state, e.g., using an infrared motion detector andinferring sleep if patient motion is reduced, or using a detected changein blood pressure, brain waves, or other parameter that is indicative ofsleep, and so on. Alternately, the cycler 14 may simply “ask” thepatient—“are you asleep?” and control system operation based on thepatient's response (or lack of response).

Patient Line State Detection Apparatus

In one aspect, a fluid line state detector detects when a fluid line toa patient, such as patient line 34, is adequately primed with fluidbefore it is connected to the patient. (It should be understood thatalthough a fluid line state detector is described in connection with apatient line, aspects of the invention include the detection of thepresence any suitable tubing segment or other conduit and/or a fillstate of the tubing segment or other conduit. Thus, aspects of theinvention are not limited to use with a patient line, as a tubing statedetector may be used with any suitable conduit.) In some embodiments, afluid line state detector can be used to detect adequate priming of atubing segment of the patient-connecting end of a fluid line. Thepatient line 34 may be connected to an indwelling catheter in apatient's blood vessel, in a body cavity, subcutaneously, or in anotherorgan. In one embodiment, the patient line 34 may be a component of aperitoneal dialysis system 10, delivering dialysate to and receivingfluid from a patient's peritoneal cavity. A tubing segment near thedistal end of the line may be placed in an upright position in a cradlewithin which the sensor elements of the detector are located. FIG. 10shows a front perspective view of an exemplary configuration of a fluidline state detector 1000, which may be mounted on, or otherwise exposedat, the left side exterior of the housing 82, e.g., to the left of thefront door 141. The fluid line state detector will be described as apatient line state detector 1000, for purposes of example. The patientline 34 should preferably be primed prior to being connected to thepatient, because air could otherwise be delivered into the patient,raising the risk of complications. It may be permissible in somesettings to allow up to 1 mL of air to be present in the patient line 34prior to being connected to a patient's peritoneal dialysis catheter.The exemplary configurations of the patient line state detector 1000described below will generally meet or exceed this standard, as they arecapable of detecting a liquid level in a properly positioned tubingsegment of line 34 so that at most about 0.2 mL of air remains in thedistal end of line 34 after priming.

In one aspect, a first configuration patient line state detector 1000may include a base member 1002. There may also be a patient line statedetector housing 1006 affixed to (or commonly molded with) the basemember 1002, such that the detector housing 1006 may extend outwardlyfrom the base member 1002. The detector housing 1006 defines a tube orconnector holding channel 1012 within which a tubing segment 34 a nearthe distal end of a patient line 34, or its associated connector 36 maybe positioned. The portion of the detector housing 1006 facing the basemember 1002 may be substantially hollow, and as a result an open cavity1008 (shown in FIG. 11 and FIG. 13) may be created behind the detectorhousing 1006. The open cavity 1008 may accommodate the placement andpositioning of sensor elements (1026, 1028, 1030 and 1032 shown in FIG.13) next to the channel 1012 within which tubing segment 34 a may bepositioned. In an alternative embodiment, there may also optionally be astabilizing tab 1010 extending outwardly from the base member 1002. Thestabilizing tab 1010 may have a concave outer shape, so that it maysubstantially conform to the curvature of the patient line connector 36when the patient line 34 is placed in the patient line state detectorhousing 1006. The stabilizing tab 1010 may help to prevent the connector36 from moving during priming of the patient line 34, increasing theaccuracy and efficiency of the priming process. The detector housing1006 may have a shape that generally helps to define the tube orconnector holding channel 1012, which in turn may have dimensions thatvary to accommodate the transition from tubing segment 34 a to tubeconnector 36.

In this illustrative embodiment, the channel 1012 may substantiallyconform to the shape of the patient line connector 36. As a result thechannel 1012 may be “U-shaped” so as to encompass a portion of theconnector 36 when it is placed into the channel 1012. The channel 1012may be made up of two distinct features; a tube portion 1014 and acradle 1016. In another aspect, the tube portion 1014 may be positionedbelow the cradle 1016. Additionally, the cradle 1016 may be formed by apair of side walls 1018 and a back wall 1020. Both of the side walls1018 may be slightly convex in shape, while the back wall 1020 may begenerally flat or otherwise may have a contour generally matching theshape of the adjacent portion of connector 36. A generally convex shapeof the side walls 1018 helps to lock the patient line connector 36 intoplace when positioned in the cradle 1016.

In an illustrative embodiment for a first configuration of patient linestate detector 1000, a region 36 a of the patient line connector 36 mayhave a generally planar surface that can rest securely against theopposing back wall 1020 of channel 1012. Additionally, this region 36 aof the connector 36 may have recesses 37 on opposing sides, which can bepositioned adjacent to the opposing side walls 1018 of channel 1012 whenthe connector 36 is positioned within the detector housing 1006. Therecesses 37 can be defined by flanking raised elements 37 a of connector36. One of these recesses 37 is partially visible in FIG. 10. The twoside walls 1018 may have a generally mating shape (such as, e.g. aconvex shape) to engage recesses 37 and to help lock connector 36 intoplace within cradle 1016. This helps to prevent the connector 36 andtubing segment 34 a from being inadvertently removed from the detectorhousing 1006 during priming of the patient line 34. If the raisedelements 37 a of connector 36 are made of sufficiently flexible material(such as, e.g., polypropylene, polyethylene, or other similarpolymer-based material) a threshold pulling force against connector 36will be capable of disengaging connector 36 and tubing segment 34 a fromthe detector housing 1006.

In another aspect, the tube portion 1014 of the cavity 1012 may surrounda majority of tubing segment 34 a at a point just before tubing segment34 a attaches to the connector 36. The tube portion 1014 may contain amajority of tubing segment 34 a using three structures: the two sidewalls 1018 and the back wall 1020. In an embodiment, the two side walls1018 and back wall 1020 may be transparent or sufficiently translucent(constructed from, e.g. plexiglass) so as to allow the light from aplurality of LED's (such as, e.g., LED's 1028, 1030, and 1032 in FIG.13) to be directed through the walls without being significantly blockedor diffused. An optical sensor 1026 (shown in FIG. 12), may also bepositioned along one of the walls 1018, and can detect the light beingemitted by the LED's. In the illustrated embodiment, a transparent ortranslucent plastic insert 1019 may be constructed to snap into the maindetector housing 1006 in the region where the LED's have been positionedin the housing.

FIG. 12 shows a perspective layout view with LED's 1028, 1030, and 1032and optical sensor 1026 surface-mounted on a patient line state detectorprinted circuit board 1022. FIG. 13 shows a plan view of LED's 1028,1030, and 1032 and optical sensor 1026 mounted on detector circuit board1022, where the detector circuit board 1022 can be positioned adjacentthe back wall 1020 and side walls 1018 of detector housing 1006. FIG. 14is an exploded perspective view of detection assembly 1000 showing therelative positions of the printed circuit board 1022 and the translucentor transparent plastic insert 1019 with respect to the housing 1006.

Referring also to the illustrative embodiment of FIG. 11, the detectorcircuit board 1022 may be positioned on a support structure 1004 andinside open cavity 1008, which was formed from detector housing 1006extending outwardly from base member 1002. The base member 1002 andsupport structure 1004 may be affixed to one another, or may be commonlymolded, so that the base member 1002 is generally perpendicular to thesupport structure 1004. This orientation generally permits the plane ofthe detector circuit board 1022 to be generally perpendicular to thelong axis of tubing segment 34 a when secured within channel 1012. Thedetector circuit board 1022 may conform generally to the cross-sectionalshape of open cavity 1008, and it may also include a cutout 1024 (FIG.12, 13) generally matching the cross-sectional shape of channel 1012formed by back wall 1020 and side walls 1018 (FIG. 10). The detectorcircuit board 1022 may then be positioned within open cavity 1008 withcutout 1024 nearly adjacent to side walls 1018 and back wall 1020 ofdetector housing 1006 in order to ensure proper alignment of thedetector circuit board 1022 with tubing segment 34 a or connector 36.

The detector circuit board 1022 may include a plurality of LED's and atleast one optical sensor, which may be attached to circuit board 1022,and in one embodiment, the LED's and optical sensor may besurface-mounted to circuit board 1022. In one aspect, the detectorcircuit board 1022 may include a first LED 1028, a second LED 1030, athird LED 1032, and an optical sensor 1026. A first LED 1028 and asecond LED 1030 may be positioned so as to direct light through the sameside wall 1018 a of channel 1012. The light emitted by the first LED1028 and the second LED 1030 may be directed in a generally paralleldirection, generally perpendicular to the side wall 1018 a to which theyare nearest. An optical sensor 1026 may be positioned along the oppositeside wall 1018 b of channel 1012. Furthermore, a third LED 1032 may bepositioned along the back wall 1020 of channel 1012. In thisillustrative embodiment, such a configuration of the LED's and theoptical sensor 1026 allows the patient line state detector 1000 todetect three different states during the course of priming the patientline 34; a tubing segment 34 a or connector 36 nearly completely filledwith fluid (primed state), an incompletely filled tubing segment 34 a orconnector 36 (non-primed state), or the absence of a tubing segment 34 aand/or connector 36 from channel 1012 (line-absent state).

When used in a peritoneal dialysis system such as, for exampleperitoneal dialysis system 10, configuring the detector circuit board1022 in this fashion allows the appropriate control signal to be sent tothe PD cycler controller system 16. Controller system 16 may then informthe user, via user interface 144, to position the distal end of line 34in the patient line state detector 1000 prior to making a connection tothe peritoneal dialysis catheter. The controller may then monitor forplacement of tubing segment 34 a within patient line state detector1000. The controller may then proceed to direct the priming of line 34,to direct termination of priming once line 34 is primed, and then toinstruct the user to disengage the distal end of line 34 from thepatient line state detector 1000 and connect it to the user's peritonealdialysis catheter.

Surface mounting the LED's 1028, 1030, and 1032 and the optical sensor1026 to the circuit board 1022 can simplify manufacturing processes forthe device, can allow the patient line state detector 1000 and circuitboard 1022 to occupy a relatively small amount of space, and can helpeliminate errors that may arise from movement of the LED's or theoptical sensor relative to each other or to the channel 1012. Were itnot for surface mounting of the sensor components, misalignment of thecomponents could occur either during assembly of the device, or duringits use.

In one aspect, the optical axis (or central optical axis) of LED 1032may form an oblique angle with the optical axis of optical sensor 1026.In the illustrated embodiment, the optical axis of a first LED 1028, asecond LED 1030, and an optical sensor 1026 are each generally parallelto each other and to back wall 1020 of channel 1012. Thus, the amount oflight directed toward optical sensor 1026 from the LED's may varydepending on the presence or absence of (a) a translucent or transparentconduit within channel 1012 and/or (b) the presence of liquid within theconduit (which, for example, may be tubing segment 34 a). Preferably,LED 1032 may be positioned near the side wall (e.g., 1018 a) that isfarthest from optical sensor 1026 in order for some of the light emittedby LED 1032 to be refracted by the presence of a translucent ortransparent tubing segment 34 a within channel 1012. The degree ofrefraction away from or toward optical sensor 1026 may depend on thepresence or absence of fluid in tubing segment 34 a.

In various embodiments, the oblique angle of LED 1032 with respect tooptical sensor 1026 creates a more robust system for determining thepresence or absence of liquid with a translucent or transparent conduitin channel 1012. LED 1032 may be positioned so that its optical axis canform any angle between 91° and 179° with respect to the optical axis ofoptical sensor 1026. Preferably the angle may be set within the range ofabout 95° to about 135° with respect to the optical sensor's opticalaxis. More preferably, LED 1032 may be set to have an optical axis ofabout 115°+/−5° with respect to the optical axis of optical sensor 1026.In an illustrative embodiment shown in FIG. 13, the angle θ of theoptical axis of LED 1032 with respect to the optical axis of opticalsensor 1026 was set to approximately 115°, +/−5°. (The optical axis ofoptical sensor 1026 in this particular embodiment is roughly parallel toback wall 1020, and roughly perpendicular to side wall 1018 b). Theadvantage of angling LED 1032 with respect to the optical axis ofoptical sensor 1026 was confirmed in a series of tests comparing theperformance of the optical sensor 1026 in distinguishing a fluid filledtube segment (wet tube) from an air filled tube segment (dry tube) usingan LED 1032 oriented at about a 115° angle vs. an LED whose optical axiswas directed either perpendicularly or parallel to the optical axis ofoptical sensor 1026. The results showed that an angled LED-based systemwas more robust in distinguishing the presence or absence of liquid intubing segment 34 a. Using an angled LED 1032, it was possible to selectan optical sensor signal strength threshold above which an empty tubingsegment 34 a could reliably be detected. It was also possible to selectan optical sensor signal strength threshold below which a liquid-filledtubing segment 34 a could reliably be detected.

FIG. 15 shows a graph of test results demonstrating the ability ofpatient line state detector 1000 to distinguish between a liquid-filledtubing segment 34 a (primed state) and an empty tubing segment 34 a(non-primed state). The results were recorded with LED 1032 (third LED)oriented at an angle of about 115° with respect to the optical axis ofoptical sensor 1026, and LED 1030 (second LED) oriented roughly parallelto the optical axis of optical sensor 1026. The results plotted in FIG.15 demonstrate that patient line state detector 1000 can reliablydiscriminate between a primed state and a non-primed state. When therelative signal strength associated with light received from LED 1030was approximately 0.4 or above, it was possible to resolve an uppersignal detection threshold 1027 and a lower signal detection threshold1029 for a non-primed vs. primed state using only the light signalreceived from LED 1032. The upper threshold 1027 can be used to identifythe non-primed state, and the lower threshold 1029 can be used toidentify the primed state. The data points located above theupper-threshold 1027 are associated with an empty tubing segment 34 a(non-primed state), and the data points located below thelower-threshold 1029 are associated with a liquid-filled tubing segment34 a (primed state). A relatively narrow region 1031 between these twothreshold values defines a band of relative signal strength associatedwith light received from LED 1032 in which an assessment of the primingstate of tubing segment 34 a may be indeterminate. A controller (suchas, e.g., control system 16) may be programmed to send the user anappropriate message whenever a signal strength associated with lightreceived from LED 1032 falls within this indeterminate range. Forexample, the user may be instructed to assess whether tubing segment 34a and/or connector 36 are properly mounted in patient line statedetector 1000. In the context of a peritoneal dialysis system, ifoptical sensor 1026 generates a signal corresponding with an emptytubing segment 34 a, the controller can direct the cycler to continue toprime patient line 34 with dialysate. A signal corresponding to aliquid-filled tubing segment 34 a can be used by the controller to stopfurther priming and instruct the user that the fluid line 34 is ready tobe connected to a dialysis catheter.

In an embodiment, the cycler controller may continuously monitor thereceived signal from one of the LED's at the initiation of the primingprocedure. Upon detection of a change in the received signal, thecontroller may halt further fluid pumping to carry out a fullmeasurement using all of the LED's. If the received signals are wellwithin the range indicating a wet tube, then further priming may behalted. However, if the received signals are within the indeterminateregion 1031 or within the ‘dry’ region, then the cycler may command aseries of small incremental pulses of fluid into the patient line by thepumping cassette, with a repeat reading of the LED signal strengthsafter each pulse of fluid. The priming can then be halted as soon as areading is achieved that indicates a fluid-filled line at the level ofthe sensor. Incremental pulses of fluid may be accomplished bycommanding brief pulses of the valve connecting the pressure reservoirto the pump actuation or control chamber. Alternatively, the controllermay command the application of continuous pressure to the pump actuationor control chamber, and command the pump's outlet valve to open brieflyand close to generate the series of fluid pulses.

FIG. 16 shows a graph of test results demonstrating the superiority ofan angled LED 1032 (LEDc) when compared with an LED (LEDd) whose opticalaxis is roughly perpendicular to the optical axis of optical sensor1026. In this case, the relative signal strength generated by opticalsensor 1026 in response to light from LEDc was plotted against thesignal strength associated with light from LEDd. Although someseparation between a liquid-filled (‘primed’) and empty (‘non-primed’)tubing segment 34 a was apparent at an LEDd relative signal strength ofabout 0.015, there remained a substantial number of ‘non-primed’ datapoints 1035 that cannot be distinguished from ‘primed’ data points basedon this threshold value. On the other hand, a relative signal strength1033 associated with light from LEDc of 0.028-0.03 can effectivelydiscriminate between ‘primed’ tubing segment 34 a (primed state) and‘non-primed’ tubing segment 34 a (non-primed state). Thus an angled LED(1032) can generate more reliable data than an orthogonally orientedLED.

In another embodiment, a patient line state detector 1000 can alsodetermine whether a tubing segment 34 a is present in channel 1012. Inone aspect, a first LED 1028 and a second LED 1030 may be positionednext to one another. One LED (e.g., LED 1028) may be positioned so thatits optical axis passes through approximately the center of a properlypositioned translucent or transparent conduit or tubing segment 34 a inchannel 1012. The second LED (e.g. LED 1030) may be positioned so thatits optical axis is shifted slightly off center with respect to conduitor tubing segment 34 a in channel 1012. Such an on-center/off-centerpairing of LED's on one side of channel 1012, with an optical sensor1026 on the opposing side of channel 1012, has been shown to increasethe reliability of determining whether a liquid conduit or tubingsegment 34 a is present or absent within channel 1012. In a series oftests in which a tubing segment 34 a was alternately absent, present butimproperly positioned, or present and properly positioned within channel1012, signal measurements were taken by the optical sensor 1026 from thefirst LED and the second LED 1030. The signals received from each LEDwere plotted against each other, and the results are shown in FIG. 17.

As shown in FIG. 17, in the majority of cases in which tubing segment 34a was absent from channel 1012 (region 1039), the signal strengthreceived by optical sensor 1026 attributable to LEDa (LEDa receptionstrength) was found not to be significantly different from the signalstrength received from LEDa during a calibration step in which LEDa wasilluminated in a known absence of any tubing in channel 1012. Similarly,the signal strength associated with LEDb (LEDb reception strength), wasfound not to be significantly different from LEDb during a calibrationstep in which LEDb was illuminated in a known absence of any tubing inchannel 1012. Patient line state detector 1000 can reliably determinethat no tube is present within channel 1012 if the ratio of LEDa to itscalibration value, and the ratio of LEDb to its calibration value areeach approximately 1±20%. In a preferred embodiment, the threshold ratiocan be set at 1+15%. In an embodiment in which patient line statedetector 1000 is used in conjunction with a peritoneal dialysis cycler,LEDa and LEDb values within region 1039 of FIG. 17, for example, can beused to indicate the absence of tube segment 34 a from channel 1012. Thecycler controller can be programmed to pause further pumping actions andinform the user via user interface 144 of the need to properly positionthe distal end of patient line 34 within patient line state detector1000.

The configuration and alignment of the three LED's and the opticalsensor 1026 described above is capable of generating the required datausing translucent or transparent fluid conduits (e.g. tubing segment 34a) having a wide range of translucence. In additional testing, patientline state detector 1000 was found to be capable of providing reliabledata to distinguish liquid from air in a fluid conduit, or the presenceor absence of a fluid conduit, using samples of tubing havingsignificantly different degrees of translucence. It was also capable ofproviding reliable data regardless of whether the PVC tubing being usedwas unsterilized, or sterilized (e.g., EtOx-sterilized).

The measurements taken by the optical sensor 1026 from the LED's can beused as inputs to a patient line state detector algorithm in order todetect the state of tubing segment 34 a. Besides detecting a full,empty, or absent tubing segment 34 a, the result of the algorithm may beindeterminate, possibly indicating movement or improper positioning ofthe tubing segment 34 a within the patient line state detector 1000, orpossibly the presence of a foreign object in channel 1012 of patientline state detector 1000. Manufacturing variations may cause the outputfrom the LED's and the sensitivity of optical sensor 1026 to vary amongdifferent assemblies. Therefore, it may be advantageous to perform aninitial calibration of the patient line state detector 1000. Forexample, the following procedure may be used to obtain calibrationvalues of the LED's and sensor:

-   -   (1) Ensure that no tubing segment 34 a is loaded in the patient        line state detector 1000.    -   (2) Poll the optical sensor 1026 in four different states:        -   (a) no LED illuminated        -   (b) first LED 1028 (LEDa) illuminated        -   (c) second LED 1030 (LEDb) illuminated        -   (d) third LED 1032 (LEDc) illuminated    -   (3) Subtract the ‘no LED illuminated’ signal value from each of        the other signal values to determine their ambient corrected        values, and store these three readings as ‘no-tube’ calibration        values.

Once calibration values for the LED's and sensor are obtained, the stateof tubing segment 34 a may then be detected. In this illustrativeembodiment, the patient line state detector algorithm performs a statedetection in a test as follows:

-   -   (1) Poll the optical sensor 1026 in four different states:        -   (a) no LED illuminated        -   (b) first LED 1028 (LEDa) illuminated        -   (c) second LED 1030 (LEDb) illuminated        -   (d) third LED 1032 (LEDc) illuminated    -   (2) Subtract the ‘no LED illuminated’ value from each of the        other values to determine their ambient corrected values.    -   (3) Calculate the relative LED values by dividing the test        values associated with each LED by their corresponding        calibration (‘no-tube’) values.

Results:

-   -   If the ambient corrected LEDa value is less than 0.10, then        there may be a foreign object in the detector, or an        indeterminate result can be reported to the user.    -   If the ambient corrected LEDa and LEDb values fall within ±15%        of their respective stored calibration (no-tube) values, then        report to the user that no tubing segment is present in the        detector.    -   If the ambient corrected LEDb value is equal to or greater than        about 40% of its stored calibration (‘no-tube’) value,        -   (a) check the signal associated with LEDc            -   (i) if the ambient corrected signal associated with LEDc                is equal or greater than about 150% of its calibration                (‘no-tube’) value, then report to the user that the                tubing segment is empty.            -   (ii) If the ambient corrected signal associated with                LEDc is equal to or less than about 125% of its                calibration (‘no-tube’) value, then report to the user                that the tubing segment is filled with liquid.            -   (iii) Otherwise, the result is indeterminate, and either                repeat the measurement (e.g., the tubing segment may be                moving, may be indented, or otherwise obscured), or                report to the user that the tubing segment should be                checked to ensure that it is properly inserted in the                detector.    -   If the ambient corrected LEDb value is less than about 40% of        its stored calibration (‘no-tube’) value, then the LEDc        threshold for determining the presence of a dry tube may be        greater. In an embodiment, for example, the LEDc empty tube        threshold was found empirically to follow the relationship:        [LEDc empty tube threshold]=−3.75×[LEDb value]+3.

Once it is determined that the tubing segment 34 a has been loaded inthe patient line state detector 1000, the patient line state detectoralgorithm can perform the following:

-   -   a) Poll the optical sensor 1026 with no LED illuminated and        store this as the no LED value.    -   b) Illuminate LEDc    -   c) Poll the optical sensor 1026, subtract the no LED value from        the LEDc value, and store this as the initial value.    -   d) Begin pumping    -   e) Poll the optical sensor 1026 and subtract the no LED value        from the subsequent LEDc value.    -   f) If this value is less than 75% of the initial value, then        conclude that tubing segment 34 a is filled with liquid, stop        pumping, confirm the detector state using the above procedure,        and when indicated, report to the user that priming is complete.        Otherwise, keep repeating the poll, calculation, and comparison.        In an embodiment, the system controller can be programmed to        perform the polling protocol as frequently as desired, such as,        for example, every 0.005 to 0.01 seconds. In an embodiment, the        entire polling cycle can conveniently be performed every 0.5        seconds.

FIG. 18 shows the results of sample calibration procedures for sixcyclers. The signal strength range that distinguishes a dry tube from awet tube (‘wet/dry threshold’ ranges) is noted to vary among thedifferent cyclers. (The variations in these ranges may be due to minorvariations in manufacturing, assembly and positioning of the variouscomponents). Thus at calibration, each cycler may be assigned a wet/drythreshold signal strength range that optimally separates the data pointsgenerated with a dry tube from the data points generated with a wettube.

FIG. 19 shows a perspective view of a second configuration of a patientline state detector 1000. Two or more different patient line statedetector configurations may be necessary to accommodate varying types ofpatient connectors. In this illustrative embodiment, the secondconfiguration patient line state detector 1000 may include most of thesame components as in the first configuration patient line statedetector 1000. However, in order to accommodate a different type ofconnector, the second configuration may include a raised element 1036above housing 1006, rather than the stabilizing tab 1010 found in thefirst configuration patient line state detector 1000. The raised element1036 may generally conform to the shape of a standard patient lineconnector cap or connector flange.

In accordance with an aspect of the disclosure, detector housing 1006may not include a tube portion 1014. Therefore, open cavity 1008 may bearranged to allow placement of detector circuit board 1022 so that theLED's and optical sensor may be positioned next to a translucent ortransparent patient line connector 36 rather than a section of tubing.Channel 1012 consequently may be shaped differently to accommodate thetransmission of LED light through connector 36.

In some embodiments, the fluid line detector 1000, rather than beingused to detect the prime state of a segment of tubing, may use one ormore LED's simply to detect the presence of the line segment in thefluid line detector 1000. The presence and proper seating of the linesegment may be determined using fewer LED's than the embodimentsdescribed above.

In other embodiments, another type of sensor may be used to detect oneor more condition of interest related to a fluid line such as a fluidline 30 or patient line 34. For example, a fluid line detector 1000 mayinclude an electrical or magnetic contact switch or physically actuatedswitch such as a microswitch. The fluid line detector 1000 may detectthe presence of a fluid line connector 36 or tubing segment 34 a withactuation of such a switch. In some embodiments, two or more suchswitches may be used in a fluid line detector 1000. This may providesome redundancy or may be used to detect that multiple line segments ofinterest are properly seated. In an embodiment, a microswitch may, forexample, be disposed in the channel 1012 so as to be actuated when thetubing segment 34 a is seated in the channel 1012. Alternatively oradditionally, a microswitch may be disposed, for example in a cradle1016, to be actuated when a fluid line connector 36 is positioned in thefluid line detector 1000. In such embodiments, a cycler controller (e.g.control system 16) may not allow priming of the tubing until all of theone or more switches indicate that the line and/or connector areproperly seated in the fluid line detector 1000.

In another embodiment, the fluid line detector 1000 may sense thepresence and state of a tube segment using a split ring resonator-basedsensor. Such a detector is shown and described, for example, in U.S.patent application Ser. No. 14/341,207, filed Jul. 25, 2014, andentitled System, Method and Apparatus for Bubble Detection in a FluidLine Using a Split-Ring Resonator, the contents of which are herebyincorporated by reference.

In some embodiments, the sensor(s) in the fluid line detector 1000 maybe configured to detect the type of fluid line 34 installed in the fluidline detector 1000 (e.g., adult vs. pediatric size, opaque vs.translucent, etc.). The fluid line connector 36 and/or tubing segment 34a may, for example, have different differentiating features (e.g.different geometries) depending on the type of line being used. Thesensor(s) in the fluid line detector 1000 may be configured to discernwhich type of line is present based upon sensing the presence or absenceof such differentiating features.

For example, if a fluid line detector 1000 is configured to usemicroswitches, the switches may be configured to detect the presence ofa particular type of fluid line connector 36. The fluid line connectors36 on each type of line may include different features (e.g. differentprojections or voids, or differently disposed projections or voids).When installed in the fluid line detector 1000, the fluid line connector36 may trip a specific switch or group of switches to detect thepresence of the particular type of fluid line connector 36. If aninvalid or unexpected combination of switches are actuated, or if acombination of switches is actuated that does not correspond to a fluidline geometry intended for use with the cycler or medical device, thecontroller may be programmed to notify the user of the incompatible orimproper line. This arrangement of switches may also be used to detectimproperly seated lines or connectors.

In other embodiments, the completion of priming of a fluid line 34 witha liquid can be inferred by detecting when liquid flow has replaced airflow in the lumen of the distal end of the line 34 or in a connector 36at the distal end of the line 34. The difference in resistance to flowbetween air and liquid in a lumen of a given caliber can be detected bymonitoring the flow rate of the liquid when under a pre-determined force(by gravity or by active pumping). The caliber of the lumen may bechosen to optimize the differentiation between air flow and liquid flow.In most cases, this will involve introducing a flow restriction near orat the end of the fluid line 34 or a distal connector. A properly chosenflow restriction at the distal end of the line 34 or connector 36 willpermit relatively unrestricted air flow out of the line 34, whileimpeding liquid flow enough to slow the advance of a liquid columnthrough the line 34. This increased liquid flow resistance or change inpressure drop across the restriction zone can be detected by the use ofa flow meter in the liquid flow path, or by measurement of the change involume of liquid in an upstream pumping chamber over a pre-determinedtime interval. In an embodiment in which a membrane-based positivedisplacement pump is used, the rate of change of liquid volume in apumping chamber can be calculated by monitoring the pressure in anactuation chamber of the pump (through the application of Boyle's Law orother pressure-volume relationships of an ideal gas in a closed space,for example), the pressure in the actuation chamber providing anindication of the pressure in the pumping chamber of the pump. Acontroller receiving liquid flow data from the fluid line, or computingliquid flow out of the pumping chamber through measurement of pressurechanges in the pumping chamber, can compare the liquid flow to apre-determined value. Alternatively, the controller can calculate a dropin liquid flow rate, and compare the change in flow rate to an expectedvalue to declare that the fluid line has been primed with liquid.

The flow-impeded zone may comprise a constriction, obstruction, partialblockage, or restriction (e.g. orifice) which allows for the easypassage of air, but impedes the passage of a liquid such as dialysatesolution. The feature may comprise a short segment of distal tubing orfluid connector 36 that includes a region having a smallercross-sectional area than that of the fluid conduit in the upstream orproximal section of the fluid line. The term ‘restriction’ as usedherein is meant to encompass any feature that increases resistance toflow differentially between air and liquid in a fluid conduit.

In an embodiment, the restriction may be removable from the distal endof the fluid line or an associated connector. For instance, therestriction may be included in a plug or cap which remains in place onthe fluid line 34 during priming of the fluid line 34. The restrictionmay, for example, be molded as part of the plug or cap duringmanufacture. This restriction may be a recess, void, channel or otherflow path in the plugging portion of the cap. The plugging portion ofthe cap may be inserted into the fluid conduit directly, or into thelumen of an attached connector 36. Alternatively, the plug or pluggingportion of the cap may be sized to have a diameter which is smaller thanthe diameter of the fluid conduit or its associated connector lumen.When the cap is installed the plug portion may obstruct part of thefluid conduit, creating a small gap between the outer surface of theplug and the inner wall of the conduit, and thereby generate therestriction.

When pumping fluid to prime a fluid line 34, fluid will move at arelatively high flow rate as air is freely displaced out of the fluidline 34 through the restriction. The increase in impedance when liquidreaches the restriction will slow the flow rate. Flow rate may bemonitored by a controller receiving input from one or more sensors aspriming occurs. When the flow rate drops, it may be inferred that theair has been pushed out of the line beyond the restriction, and that agiven applied force is now attempting to push liquid through therestriction. In some embodiments, the controller may employ additionallogic to discern between a number of possible causes for reduced liquidflow rates in the fluid line.

In embodiments in which the restriction is an orifice (positioned eitherat the distal end of the fluid line or within an attached connector),the cross-sectional area of the orifice opening may be selected so as togenerate a desired amount of impedance to liquid flow. Additionally, thepumping pressure chosen may be selected such that the flow rates whenpumping air and when pumping liquid are detectably different.

It may be desirable to place the restriction slightly upstream of thepoint at which a fluid line 34 would be fully primed. This would allowfor some liquid to flow through the restriction during a determinationor recognition period over which a controller is determining whether theimpedance to liquid flow has changed. Having a line volume downstreamfrom the restriction provides a fluid buffer to accumulate additionalliquid while the controller makes a determination of priming and stopsthe fluid pump, thus helping to prevent overflow of liquid out of thedistal end of the fluid line. Preferably, the delay characteristics ofthe pumping system in responding to a change in liquid flow impedanceare determined empirically for the system once the system parametershave been selected. These parameters may include, for example, the forceor pressure applied by the pump, the frequency of pumping volumedeterminations or flow rate measurements, the caliber and length of thetubing, the properties of the flow restriction, and the response timesof the controller and pump. Once the system characteristics aredetermined, the post-restriction tubing or connector buffer volumeneeded to prevent overflow can be determined empirically. Forillustrative purposes, if the flow rate through a restriction is 30mL/min, and it takes about 5 seconds for the controller and pump torecognize and respond to the impedance change, a hysteretic fluid volumeof about 2.5 mL would be moved while the system responds to theimpedance change. In such an embodiment, the downstream volume beyondthe restriction may be set to approximately 2.5 mL or slightly more than2.5 mL. This may serve to help minimize the amount of air left in thefluid line 34 during priming without over-priming the line and causingfluid to overflow the line and spill out.

Alternatively, the restriction may extend along the line axis for adistance that allows the restriction flow pathway volume toapproximately the flow volume anticipated while the impedance change isbeing detected. This embodiment may be desirable when the restriction isincluded in a fluid line cap.

In some embodiments, an air permeable, but substantially liquidimpermeable material may be used to restrict liquid flow. Such amaterial may allow for relatively unrestricted passage of air, butrestrict or prevent passage of liquid. This material may be placed atthe end of the fluid line 34 and may allow for air to be pumped out ofthe line 34, but prevent overflowing and spilling when the line 34reaches primed state. The material may then, for example, be removedalong with a fluid line cap when a user uncaps the line. In somespecific embodiments, the material used may be Goretex or anothersimilar material (e.g., breathable materials that may be eithermicroporous or macroporous). As above, a drop in flow rate when theliquid reaches the material would signal that the fluid line 34 hasreached a primed state.

FIG. 20 and FIG. 21 depict an example representative embodiment of afluid line cap 5320, fluid line 34 and a fluid line connector 36. Asshown, a restriction 5322 is included in the fluid line 34. In otherexamples, the cap 5320 may have inside surface features that incorporaterestriction similar to the restriction 5322 shown. In this example, therestriction 5322 is optionally positioned such that there is some fluidline 34 volume downstream of the restriction 5322. The restriction 5322in the example embodiment is a section in the fluid path with a reducedcross sectional area. In other examples, the restriction 5322 may be anorifice or a membrane which is slit, perforated, or otherwise has one ormore pores to increase the resistance to the passage of liquid.

As illustrated in FIG. 20 the liquid 5324 in the fluid line 34 has notyet reached the restriction 5322. At this point, the flow rate of fluidthrough the fluid line 34 (e.g. a stratified column of air and liquid)may be relatively high. Once the air column has been evacuated, liquid5324 in the fluid line 34 will have reached the restriction 5322. Atthis point, the flow rate will drop due to an impedance change. Someliquid 5324 will continue to flow as the cycler determines that theimpedance has changed. Once detected, the cycler may be programmed tostop the flow of liquid through the line. At this point, and as shown inFIG. 21, the liquid 5324 will have substantially primed the entire line34 including the line 34 volume downstream of the restriction 5322. Thecontroller may be programmed to notify a user that the line 34 has beenprimed and is ready for connection to a catheter or other device inpreparation for treatment.

FIG. 22 and FIG. 23 depict another example embodiment of a fluid line34, fluid line connector 36, and a fluid line cap 5320. As shown, thereis no restriction in the fluid line 34 or fluid line connector 36. Thefluid line cap 5320 acts as plug for the fluid line 34 and includes arestriction 5322. In the example embodiment, the restriction 5322 maycomprise a notch, groove, or channel recessed into the circumference ofthe plugging portion of the fluid line cap 5320. The restriction 5322may be sized to allow air to be pumped out of the line at relativelylittle resistance during priming, but impede the flow of liquid when theair column has been fully expelled. When the controller determines thatthe line 34 is primed, the controller may then instruct a user to removeline cap 5320 and attach the fluid line connector 36 to an indwellingcatheter or other similar device.

As illustrated in FIG. 22 the liquid 5324 in the fluid line 34 has notyet reached the restriction 5322. At this point, the flow rate of fluid(gas plus liquid) through the fluid line 34 may be relatively high. Oncethe liquid 5324 in the fluid line 34 reaches the restriction 5322, theflow rate will drop due to an impedance change between gas flow andliquid flow through the restriction 5322. Some liquid 5324 will continueto flow as the controller determines that the impedance has changed.Once detected, the controller will stop the flow of liquid 5324 throughthe line. At this point, and as shown in FIG. 23, the liquid 5324 willhave substantially primed the entire line 34. The controller may thennotify a user that the line 34 has been primed and that the line cap5320 may be removed. With the cap 5320 removed, any excess liquid 5324pumped may fill the volume of the fluid line 34 which was previouslyoccupied by the plugging portion of the fluid line cap 5320.Alternatively, the controller may be programmed to receive a signal fromthe user that the cap 5320 has been removed, and the controller may beprogrammed to cause the cycler or pump to advance a small quantity ofliquid down the fluid line 34 to top off the distal end of the line 34or connector 36 prior to its use.

FIG. 24 depicts a representative example of a fluid line cap 5320 with aplug or plug portion 5500. As shown, the fluid line cap 5320 includes aplug portion 5500 which may be sized to project into and snuggly fit inthe fluid conduit of the fluid line 34. A notch is recessed into theplug portion 5500 of the fluid line cap 5320 and serves to create arestriction 5322 when the fluid line cap 5320 is installed on the end ofthe fluid line 34 or a line connector 36. In the illustration, the notchis substantially triangular in cross-section. In other embodiments, anysuitable cross sectional geometry may be used. Other arrangements may beused; such as, for example, a narrow lumen through the length of anotherwise solid plug 5500. Also as shown in FIG. 24, the end of the plugportion 5500 which extends into the fluid flow path may optionally berounded (or tapered). This may facilitate placing a fluid line cap 5320onto a fluid line 34.

FIG. 25 depicts another embodiment of a fluid line cap 5320. Similar toFIG. 24, the fluid line cap 5320 includes a plug portion 5500 which maybe sized to project into and snuggly fit in the fluid conduit of thefluid line 34. The restriction 5322 in FIG. 25 is a flow path whichallows for fluid to flow from the fluid conduit of the fluid line 34,through the interior of the plug portion 5500 and into an inner volumeof a fluid line connector 36. A cross-sectional view taken on alongitudinal plane of the example fluid line cap 5320 is shown in FIG.26. The cross-sectional area of the flow path is less than that of thefluid line 34 fluid conduit.

FIG. 27 shows another embodiment of a fluid line cap 5320 installed onthe fluid line connector 36 of a fluid line 34. As shown in FIG. 28 across-section taken at line 28-28 of FIG. 27, the fluid line connector36 includes a segment which extends into the fluid conduit of the fluidline 34. The tube of the fluid line 34 may be fixed (e.g. glued, bonded,welded, etc.) to the fluid line connector 36. The fluid line connector36 includes a flow path which leads from the fluid conduit of the fluidline 34 to a connector fitting 5502 included as part of the fluid lineconnector 36. The connector fitting 5502 may mate with a cooperatingfeature on a complementary connector (e.g., of a patient's indwellingcatheter) to allow for fluid to be delivered and/or withdrawn from asite (e.g., peritoneal cavity or another body cavity). In the exampleembodiment, a Luer lock is shown; however, any of a number of othersuitable connectors or fittings may be used.

The cap in the example embodiment includes a plug portion 5500. The plugportion 5500 is sized so as to extend into the fluid pathway of thefluid line connector 36. In the example embodiment, the diameter of theplug portion 5500 is smaller than the diameter of the flow path in thefluid line connector 36. When the plug portion 5500 of the fluid linecap 5320 is installed into the flow path of the fluid line connector 36,a small gap remains between the outer surface of the plug portion 5500and the inner wall of the flow path. Thus, the plug portion 5500 servesto reduce the cross-sectional area of the flow path and creates arestriction 5322.

As described above, in some embodiments, a small gap between the outersurface of the plug portion 5500 and the inner wall of the flow pathneed not be present. Instead, the plug portion 5500 may fit snuggly inthe flow path. A notch may be recessed into the outer surface of theplug portion 5500 to reduce the cross sectional area of the flow pathand create the restriction, or an otherwise solid plug inserted in theconnector lumen may include a narrow flow path to create a restrictedflow path.

In one aspect, the change in fluid flow impedance may be determinedbased on a flow rate estimation during the progression of a pumpingstroke from a pumping cassette. Additionally, a stroke displacementestimation may be used to discriminate between a change in flow rate dueto an empty pumping chamber and a change in flow rate due to liquid 5324reaching the restriction 5322 in the fluid line 34. Estimation of flowrate and stroke displacement during the progression of a pumping strokewill be further described below.

In some embodiments, a controller algorithm to estimate strokedisplacement may be used to stop a stroke prior to the full chamberbeing delivered to a fluid line. That is, a controller may be programmedto instruct a pump to perform partial delivery strokes during priming soas to avoid having the pump diaphragm reach an end-of-stroke position.This may help to ensure that any drop in flow rate is not attributableto a pump diaphragm having reached the rigid pumping chamber wall at theend of a pump stroke. When the controller determines that the volume offluid pumped per unit of time has decreased beyond a predeterminedthreshold value, the liquid 5324 in the fluid line 34 may be assumed tohave reached the restriction 5322, and the line may be deemed to havebeen primed.

In other embodiments, a controller may direct the pump to pump fluiduntil a flow rate discontinuity is detected. At this point, thecontroller may direct the pumping apparatus (e.g., cycler) to attempt todeliver a small volume of fluid from another pump chamber of a dual pumpcassette. In the event that the flow discontinuity was due to the pumpdiaphragm reaching end-of-stroke, flow from the other chamber should begreater than the ending flow rate from the first chamber. If thediscontinuity is due to a primed line condition, flow rate from theother chamber will be similar to that of the ending flow rate from thefirst chamber. Thus the device controller may determine that the linehas been primed.

In some embodiments, a nominal interior tubing volume for a fluid line34 may be determined. A controller may then direct a pump to move fluiddown the line 34 until the volume of the fluid primed down the line 34is within one chamber volume of the nominal tubing volume. Once theremaining volume of the line 34 is determined to be less than the volumeof a full pump stroke, the controller may register the next flow ratediscontinuity as indicative of a primed condition.

The nominal interior volume of the line 34 may be determined based onthe type of set being used. For example, a pediatric set may have asmaller interior tubing volume than an adult set. In some embodiments, adevice controller may determine this information via an optical sensor.In some embodiments the set may include a bar code or data matrix thatcan be read by a camera on the pumping device or cycler, the encodedinformation allowing the controller to determine the type of setinstalled. A controller receiving input from a camera may also becapable of detecting different features or geometries of a portion of aset. For example, the fluid line connector 36 may have unique,detectable geometries detectable by a fluid line detector 1000 asdescribed above. Alternatively, a user may manually enter information ona user interface of the pumping device about the type of tubing or pumpcassette in use.

Line Priming

To reduce the time needed to prime a line, it may be preferable to havethe pumping device actively prime the line rather than allowinggravity-based flow to accomplish the task. In Gravity-based priming,which is a standard procedure, fluid flow through the line depends onthe head height of the reservoir in which the priming fluid is stored.The flow rate of the fluid through the line during prime will increasewith an increase in head height of the prime fluid reservoir. Activelypriming the line through the use of one or more pumps may allow apumping device or cycler to simulate various head heights for areservoir while the reservoir remains in a fixed position. If the fluidpump includes pumping chamber(s) which are actuated pneumatically, theamount of pneumatic pressure applied to the pumping chamber(s) via adiaphragm can control the flow rate to a desired value withoutrelocating the priming reservoir. Avoiding having to relocate a fluidreservoir helps to keep the pumping or dialysis system compact, reducesthe setup burden on a user, and allows for relative fast priming offluid lines.

In some embodiments in which flow paths and chambers of a pump cassetteare to be primed with fluid, priming may be performed in two or morephases. In the first phase, the line may be primed with a lowereffective head height (e.g., lower pump pressure or by passive gravityflow) than in a second or subsequent phase. Turbulence of a higher flowrate may lead to introduction or trapping of air bubbles or pockets invarious locations or recesses of a pump cassette. This problem can bemitigated by allowing the pump cassette to be primed slowly, andsubsequently proceeding to a more rapid priming process once the fluidreaches a fluid line downstream of the cassette. The length of the firstphase may be predetermined empirically through testing, or bymeasurement of the amount of fluid volume moved from the primingreservoir to the cassette or attached fluid line.

Reducing air bubble formation or trapping is desirable for a number ofreasons, including that a line priming sensor may detect the air bubblesand lead the controller to stop the process and issue a user alert.

The duration of the first priming phase may depend on the type ofcassette being used (number of pumps and valves, and complexity of flowpaths), and the volume of its interior fluid paths and pump chambers.Preferably, the priming is performed to allow fluid to displace air fromthe cassette from bottom to top, and at a sufficiently slow rate toensure that most or all of the enclosed air is forced into the attachedfluid line and then expelled into the environment.

FIG. 29 depicts a flowchart detailing a number of steps a controller mayuse to control the priming of a cassette and attached line using twophases. In the example, the line primed is a patient line extending froma pump cassette to a patient. The steps shown may readily be generalizedfor priming of other fluid lines. As shown, in step 5570, the cyclerbegins priming the patient line by gravity feeding fluid into the linethrough the cassette. In the example embodiment, the priming reservoiris a heater bag. Free flow may be accomplished by controlling valves ofthe cassette so that an open flow path between the patient line and theheater bag is created.

When the priming operation begins in step 5570, the controller mayinitiate a timer for the first priming phase. The duration of the firstpriming phase can be determined empirically through testing so that itis sufficient to ensure that any air in the cassette has been flushedout of the cassette and into the patient line. Using the example of thecassette depicted in FIG. 3, this duration may range from 1-3 seconds.In one embodiment, the timer may be set to about 1.6 seconds. In controlsystem embodiments that do not use a timer, but rather transition out ofthe first priming phase when a pre-determined volume of fluid has beentransferred out of the priming reservoir, the pre-determined volume mayamount to approximately 1-3 ml, given the example cassette shown in FIG.3.

When the timer has elapsed (or the pre-determined volume has beentransferred), the pumping apparatus or cycler may proceed to step 5572and begin actively priming the line. Preferably step 5572 primes theline at a faster flow rate than step 5570. The cycler may continue toactively prime the patient line until a prime sensor indicates that theline has reached a fully primed state. In some embodiments, thecontroller may then signal a user on a user interface that the priminghas completed and the primed line is ready to be connected.

Solution Line Organizer

FIG. 30, FIG. 31, and FIG. 32, show a perspective view of the front ofan unloaded organizer 1038, a perspective view of the back of anunloaded organizer 1038, and a perspective view of a loaded organizer1038 respectively. In this embodiment, the organizer 1038 may besubstantially formed from a moderately flexible material (such as, e.g.,PAXON AL55-003 HDPE resin). Forming the organizer 1038 from this oranother relatively flexible polymer material increases the organizer's1038 durability when attaching and removing solution lines or solutionline connectors.

The organizer 1038 may conveniently be mounted or attached to an outerwall of the cycler housing 82. The organizer 1038 may include a tubeholder section 1040, a base 1042, and a tab 1044. The tube holdersection 1040, the base 1042, and the tab 1044 may all be flexiblyconnected, and may be substantially formed from the same HDPE-basedmaterial. The tube holder section 1040 may have a generally rectangularshape, and may include a generally flat top edge and a bottom edge thatmay be slightly curved in an outwardly direction. The tube holdersection 1040 may include a series of recessed segments 1046 that extendhorizontally along the bottom edge of the tube holder section 1040. Eachof the recessed segments 1046 may be separated by a series of supportcolumns 1048, which may also define the shape and size of the segments1046. The tube holder section 1040 may also include a raised area thatextends horizontally along the top edge of the tube holder section 1040.The raised area may include a plurality of slots 1050. The slots 1050may be defined in a vertical orientation, and may extend from the topedge of the tube holder section 1040 to the top of the recessed segments1046. The slots 1050 may have a generally cylindrical shape so as toconform to the shape of a drain line 28, solution line 30, or patientline 34. The depth of the slots 1050 may be such that the opening of theslot 1050 is narrower then the inner region of the slot 1050. Therefore,once a line is placed into the slot 1050 it becomes locked or snap-fitinto place. The line may then require a pre-determined minimum amount offorce to be removed from the slot 1050. This ensures that the lines arenot unintentionally removed from the organizer 1050.

In one aspect, the tab 1044 may be flexibly connected to the top edge ofthe tube holder section 1040. The tab 1044 may have a generallyrectangular shape. In another embodiment, the tab 1044 may also includetwo slightly larger radius corners. The tab 1044 may also include twovertically extending support columns 1048. The support columns 1048 maybe connected to the top edge of the tube holder section 1040, and mayextend in an upward direction into the tab 1044. In alternativeembodiment, the length and number of the support columns 1048 may varydepending on the desired degree of flexibility of the tab 1044. Inanother aspect, the tab 1044 may include a ribbed area 1052. The purposeof the tab 1044 and the ribbed area 1052 is to allow the organizer 1038to be easily grasped by a user so that the user can easily install,transport, or remove the solution lines 30 from the organizer 1038.Also, the tab 1044 provides an additional area of support when removingand loading the lines into the organizer 1038.

In another aspect, the base 1042 may be flexibly connected to the bottomedge of the tube holder section 1040. The base 1042 may have a generallyrectangular shape. In another embodiment, the base 1042 may also includetwo slightly larger radius corners. The base 1042 may include anelongated recessed segment 1046, which may be defined by a support ring1054 that surrounds the recessed segment 1046. The support columns 1050,the support ring 1054, and the raised area may all create a series ofvoids 1056 along the back of the organizer 1038 (shown, e.g., in FIG.31).

FIG. 33 and FIG. 34 show a perspective view of an organizer clip 1058,and a perspective view of an organizer clip receiver 1060 respectively.In these illustrative embodiments, the clip 1058 may be made from arelatively high durometer polyurethane elastomer, such as, for example,80 Shore A durometer urethane. In an alternative embodiment, the clip1058 may be made from any type of flexible and durable material thatwould allow the organizer 1038 to flex and pivot along the base 1042when positioned in the clip 1058. The clip 1058 may be “U-shaped”, andmay include a back portion that extends slightly higher than a frontportion. Additionally, there may be a lip 1062 that extends along thetop edge of the front portion of the clip 1058. The lip 1062 extendsslightly into the cavity of the clip 1058. The back portion of the clip1058 may also include a plurality of elastomeric pegs 1064 connected to(or formed from) and extending away from the back portion of the clip1058. The pegs 1064 may include both a cylindrical section 1066 and acone 1068. The cylindrical section 1066 may connect to the back portionof the clip 1058, and the cone 1068 may be attached to an open end ofthe cylindrical section 1066. The pegs 1064 allow the clip 1058 to bepermanently connected to the organizer clip receiver 1060, by engagingthe pegs 1064 within a plurality of holes 1070 in the organizer clipreceiver 1060.

The organizer clip receiver 1060 may include a plurality of chamferedtabs 1072. The chamfered tabs 1072 may mate with corresponding slots onthe back portion of the clip 1058 when the pegs 1064 are engaged withthe organizer clip receiver 1060. Once the chamfered tabs 1072 engagethe slots, they can extend through the back portion of the clip 1058,and act as locking mechanisms to hold the organizer 1038 in place whenpositioned into the clip 1058. When the organizer 1038 is positionedwithin the clip 1058, the chamfers 1072 fit into the void 1056 on theback of the base 1042, which was created by the raised support ring1054. Referring again to FIG. 31, and in accordance with another aspectof the present disclosure, there may be a plurality of ramps 1074extending outwardly from the back of the organizer 1038. The ramps 1074may be generally shaped as inclined planes. This allows the organizer1038 to angle away from the cycler 14 when placed into the clip 1058,which provides numerous advantages over previous designs. For example,in this illustrative embodiment, the angle of the organizer 1038 ensuresthat neither the tab 1044, nor any of the lines (or line caps) connectedto the organizer 1038 are allowed to interfere with the heater lid 143when the lid 143 is being opened and closed. Additionally, the angle ofthe organizer 1038 in relation to the cycler 14, coupled with theflexibility of the organizer 1038, both encourage the user to remove thesolution lines 30 from the bottom instead of from the connector end 30 aof the solution lines. Preferably, the user should not remove thesolution lines 30 by grasping the connector ends 30 a, because in doingso the user could inadvertently remove one or more caps 31, which couldcause contamination and spills. Another advantage of the organizer 1038is that it aids the user in connecting color coded solution lines 30 tothe correct containers 20 by helping to separate the color coded lines30.

Door Latch Sensor

FIG. 35, shows a perspective view of a door latch sensor assembly 1076.In this illustrative embodiment, the door latch sensor assembly 1076 mayinclude a magnet 1078 that is attached or connected to door latch 1080,and can pivot with door latch 1080 as it pivots into and our of alatching position with its mating base unit catch 1082. A sensor (notshown in FIG. 35) may be positioned behind the front panel 1084 ofcycler 14, near base unit catch 1082, to detect the presence of magnet1078 as door latch 1080 engages with base unit catch 1082. In oneembodiment, the sensor may be an analog Hall effect sensor. The purposeof the door latch sensor assembly 1076 is to confirm both that the door141 is closed and that the door latch 1080 is sufficiently engaged withcatch 1082 to ensure a structurally sound connection. FIG. 36 shows across-sectional view of the door latch sensor assembly 1076. Sensor 1079is positioned on a circuit board 1077 behind front panel 1084. Sensor1079 is preferably oriented off-axis from the line of motion of magnet1078, because in this orientation, sensor 1079 is better able to resolvea variety of positions of magnet 1078 as it approaches front panel 1084as door 141 is closed.

In one example, the door 141 may be considered to be sufficientlyengaged when the door latch 1080 has at least a 50% engagement with thecatch 1082. In one embodiment, the door latch 1080 may engage to adegree of approximately 0.120 inch nominally. Additionally, the sensor1079 may only sense a closed door 141 when the door latch 1080 issufficiently engaged with the catch 1082. Therefore, the sensor 1082 mayonly sense a closed door 141 when the door latch 1080 is engaged to adegree of approximately 0.060 inch. These engagement thresholds for thedoor latch 1080 may be set approximately at the middle range foracceptable engagement between the door latch 1080 and the catch 1082.This can help to ensure a robust design by accounting for sensor driftdue to time, temperature, and other variations. Testing was conducted todetermine the robustness of the sensor 1082 by collecting numerousmeasurements both at room temperature (approximately 24° C.) and at anabnormally cold temperature (approximately −2° C. to 9° C.). The roomtemperature readings were repeatedly higher than the cold readings, butonly by a small percentage of the 0 inch to 0.060 inch range.

In one aspect, the output of the sensor 1079 may be ratiometric to thevoltage supplied. Therefore, both the supply voltage and the output ofthe sensor 1079 may be measured (see formulas below, where the supplyvoltage and the output of the sensor 1079 are represented by Door_Latchand Monitor_5V0 respectively). Both the output of the sensor 1079 aswell as the voltage supplied may then pass through ¼ resistor dividers.Dividing the output of the sensor 1079 and the voltage supplied mayallow for a stable output to be produced. This procedure may ensure thatthe output remains stable even if the supply voltage fluctuates.

In another aspect, the sensor 1079 may respond to both positive andnegative magnetic fields. Consequently, if there is no magnetic field,the sensor 1079 may output half the supply voltage. Additionally, apositive magnetic field may cause the output of the sensor 1079 toincrease, while a negative magnetic field may result in a decrease ofthe output of the sensor 1079. In order to obtain an accuratemeasurement of the output from the sensor 1079, the magnet polarity canbe ignored, and the supply voltage can simultaneously be compensatedfor. The following formula may be used to calculate the latch sensorratio:Latch Sensor Ratio=absolute value((VDoor_Latch/VMonitor_5V0)−noFieldRatio)  (1)

Where the noFieldRatio is calculated by (VDoor_Latch/VMonitor_5V0) withthe door 141 fully open.

Using this formula:Ratio=0.0 indicates no magnetic fieldRatio>0.0 indicates some magnetic field; direction indeterminate.

Shims of various thicknesses may be used between the inside of door 141and front panel 1084 to vary the degree of engagement between latch 1080and catch 1082, in order to calibrate the strength of the magnetic fielddetected by sensor 1079 with various positions of engagement of the doorlatch assembly 1076. In one embodiment, this data can be used to developfield strength ratios with and without a shim, or in other embodimentswith several shims of varying thicknesses. In one example, the doorlatch sensor assembly 1076 may complete the procedure for determining ifthe door latch 1080 is sufficiently engaged with the catch 1082 byperforming the following:

Calculate the nearRatio and the farRatio:nearRatio=noShimRatio−(0.025/0.060)×(noShimRatio−withShimRatio)  (2)farRatio=noShimRatio−(0.035/0.060)×(noShimRatio−withShimRatio)  (3)

In an embodiment, the door latch sensor assembly 1076 may save thenoFieldRatio, nearRatio, and farRatio to a calibration file. The doorlatch sensor assembly 1076 may then load the noFieldRatio, nearRatio,and farRatio from the calibration file, and the sensor assembly 1076 maythen use the nearRatio and farRatio as the hysteresis limits for thesensor 1079. The door latch sensor assembly 1076 may then begin with theinitial condition that the door 141 is open, and then repeatedlycalculate the Latch Sensor Ratio. If the Latch Sensor Ratio is greaterthan the nearRatio, the door latch sensor assembly 1076 will change thelatch state to closed, and if the Latch Sensor Ratio is less than thefarRatio, the door latch sensor assembly 1076 will change the latchstate to open. In an alternative embodiment for the door latch sensorassembly 1076, a middleRatio can be calculated from the calibration databy averaging the noShimRatio and the withShimRatio. In this case,measurements greater than the middleRatio indicate that the door latch1080 is engaged, and measurements less than the middleRatio indicatethat the door latch 1080 is not engaged.

Set Loading and Operation

FIG. 37 shows a perspective view of the APD system 10 of FIG. 1 with thedoor 141 of the cycler 14 lowered into an open position, exposing amounting location 145 for the cassette 24 and a carriage 146 for thesolution lines 30. (In this embodiment, the door 141 is mounted by ahinge at a lower part of the door 141 to the cycler housing 82.) Whenloading the set 12, the cassette 24 is placed in the mounting location145 with the membrane 15 and the pump chamber side of the cassette 24facing upwardly, allowing the portions of the membrane 15 associatedwith the pump chambers and the valve ports to interact with a controlsurface 148 of the cycler 14 when the door 141 is closed. The mountinglocation 145 may be shaped so as to match the shape of the base member18, thereby ensuring proper orientation of the cassette 24 in themounting location 145. In this illustrative embodiment, the cassette 24and mounting location 145 have a generally rectangular shape with asingle larger radius corner which requires the user to place thecassette 24 in a proper orientation into the mounting location 145 orthe door 141 will not close. It should be understood, however, thatother shapes or orientation features for the cassette 24 and/or themounting location 145 are possible.

In accordance with an aspect of the invention, when the cassette 24 isplaced in the mounting location 145, the patient, drain and heater baglines 34, 28 and 26 are routed through a channel 40 in the door 141 tothe left as shown in FIG. 37. The channel 40, which may include guides41 or other features, may hold the patient, drain and heater bag lines34, 28 and 26 so that an occluder 147 may selectively close/open thelines for flow. Upon closing of door 141, occluder 147 can compress oneor more of patient, drain and heater bag lines 34, 28 and 26 againstoccluder stop 29. Generally, the occluder 147 may allow flow through thelines 34, 28 and 26 when the cycler 14 is operating (and operatingproperly), yet occlude the lines when the cycler 14 is powered down(and/or not operating properly). Occlusion of the lines may be performedby pressing on the lines, or otherwise pinching the lines to close offthe flow path in the lines. Preferably, the occluder 147 may selectivelyocclude at least the patient and drain lines 34 and 28.

When the cassette 24 is mounted and the door 141 is closed, the pumpchamber side of the cassette 24 and the membrane 15 may be pressed intocontact with the control surface 148, e.g., by an air bladder, spring orother suitable arrangement in the door 141 behind the mounting location145 that squeezes the cassette 24 between the mounting location 145 andthe control surface 148. This containment of the cassette 24 may pressthe membranes 15 and 16 into contact with walls and other features ofthe base member 18, thereby isolating channels and other flow paths ofthe cassette 24 as desired. The control surface 148 may include aflexible gasket or membrane, e.g., a sheet of silicone rubber or othermaterial that is associated with the membrane 15 and can selectivelymove portions of the membrane 15 to cause pumping action in the pumpchambers 181 and opening/closing of valve ports of the cassette 24. Thecontrol surface 148 may be associated with the various portions of themembrane 15, e.g., placed into intimate contact with each other, so thatportions of the membrane 15 move in response to movement ofcorresponding portions of the control surface 148. For example, themembrane 15 and control surface 148 may be positioned close together,and a suitable vacuum (or pressure that is lower relative to ambient)may be introduced through vacuum ports suitably located in the controlsurface 148, and maintained, between the membrane 15 and the controlsurface 148 so that the membrane 15 and the control surface 148 areessentially stuck together, at least in regions of the membrane 15 thatrequire movement to open/close valve ports and/or to cause pumpingaction. In another embodiment, the membrane 15 and control surface 148may be adhered together, or otherwise suitably associated.

In some embodiments, the surface of the control surface 148 or gasketfacing the corresponding cassette membrane overlying the pump chambersand/or valves is textured or roughened. The texturing creates aplurality of small passages horizontally or tangentially along thesurface of the gasket when the gasket is pulled against the surface ofthe corresponding cassette membrane. This may improve evacuation of airbetween the gasket surface and the cassette membrane surface in thetextured locations. It may also improve the accuracy of pump chambervolume determinations using pressure-volume relationships (such as, forexample, in the FMS procedures described elsewhere), by minimizingtrapped pockets of air between the gasket and the membrane. It may alsoimprove the detection of any liquid that may leak into the potentialspace between the gasket and the cassette membrane. In an embodiment,the texturing may be accomplished by masking the portions of the gasketmold that do not form the portions of the gasket corresponding to thepump membrane and valve membrane locations. A chemical engraving processsuch as the Mold-Tech® texturing and chemical engraving process may thenbe applied to the unmasked portions of the gasket mold. Texturing mayalso be accomplished by any of a number of other processes, such as, forexample, sand blasting, laser etching, or utilizing a mold manufacturingprocess using electrical discharge machining.

Before closing the door 141 with the cassette 24 loaded, one or moresolution lines 30 may be loaded into the carriage 146. The end of eachsolution line 30 may include a cap 31 and a region 33 for labeling orattaching an indicator or identifier. The indicator, for example, can bean identification tag that snaps onto the tubing at indicator region 33.In accordance with an aspect of the invention and as will be discussedin more detail below, the carriage 146 and other components of thecycler 14 may be operated to remove the cap(s) 31 from lines 30,recognize the indicator for each line 30 (which may provide anindication as to the type of solution associated with the line, anamount of solution, etc.) and fluidly engage the lines 30 with arespective spike 160 of the cassette 24. This process may be done in anautomated way, e.g., after the door 141 is closed and the caps 31 andspikes 160 are enclosed in a space protected from human touch,potentially reducing the risk of contamination of the lines 30 and/orthe spikes 160 when connecting the two together. For example, uponclosing of the door 141, the indicator regions 33 may be assessed (e.g.,visually by a suitable imaging device and software-based imagerecognition, by RFID techniques, etc.) to identify what solutions areassociated with which lines 30. The aspect of the invention regardingthe ability to detect features of a line 30 by way of an indicator atindicator region 33 may provide benefits such as allowing a user toposition lines 30 in any location of the carriage 146 without having anaffect on system operation. That is, since the cycler 14 canautomatically detect solution line features, there is no need to ensurethat specific lines are positioned in particular locations on thecarriage 146 for the system to function properly. Instead, the cycler 14may identify which lines 30 are where, and control the cassette 24 andother system features appropriately. For example, one line 30 andconnected container may be intended to receive used dialysate, e.g., forlater testing. Since the cycler 14 can identify the presence of thesample supply line 30, the cycler 14 can route used dialysate to theappropriate spike 160 and line 30. As discussed above, since the spikes160 of the cassette 24 all feed into a common channel, the input fromany particular spike 160 can be routed in the cassette 24 in any desiredway by controlling valves and other cassette features.

With lines 30 mounted, the carriage 146 may be moved to the left asshown in FIG. 37 (again, while the door 141 is closed), positioning thecaps 31 over a respective spike cap 63 on a spike 160 of the cassette 24and adjacent a cap stripper 149. The cap stripper 149 may extendoutwardly (toward the door 141 from within a recess in the cycler 14housing) to engage the caps 31. For example, the cap stripper 149 mayinclude five fork-shaped elements that engage with a correspondinggroove in the caps 31, allowing the cap stripper 149 to resistleft/right movement of the cap 31 relative to the cap stripper 149. Byengaging the caps 31 with the cap stripper 149, the caps 31 may alsogrip the corresponding spike cap 63. Thereafter, with the caps 31engaged with corresponding spike caps 63, the carriage 146 and capstripper 149 may move to the right, removing the spike caps 63 from thespikes 160 that are engaged with a corresponding cap 31. One possibleadvantage of this arrangement is that spike caps 63 are not removed inlocations where no solution line 30 is loaded because engagement of thecap 31 from a solution line 30 is required to remove a spike cap 63.Thus, if a solution line 30 will not be connected to a spike 160, thecap on the spike 160 is left in place. The cap stripper 149 may thenstop rightward movement (e.g., by contacting a stop), while the carriage146 continues movement to the right. As a result, the carriage 146 maypull the terminal ends of the lines 30 from the caps 31, which remainattached to the cap stripper 149. With the caps 31 removed from thelines 30 (and the spike caps 63 still attached to the caps 31), the capstripper 149 may again retract with the caps 31 into the recess in thecycler 14 housing, clearing a path for movement of the carriage 146 andthe uncapped ends of the lines 30 toward the spikes 160. The carriage146 then moves left again, attaching the terminal ends of the lines 30with a respective spike 160 of the cassette 24. This connection may bemade by the spikes 160 piercing an otherwise closed end of the lines 30(e.g., the spikes 160 may pierce a closed septum or wall in the terminalend), permitting fluid flow from the respective containers 20 to thecassette 24. In an embodiment, the wall or septum may be constructed ofa flexible and/or self-sealing material such as, for example, PVC,polypropylene, or silicone rubber.

In accordance with an aspect of the invention, the heater bag 22 may beplaced in the heater bag receiving section (e.g., a tray) 142, which isexposed by lifting a lid 143. In this embodiment, the cycler 14 includesa user or operator interface 144 that is pivotally mounted to thehousing 82, as discussed below. To allow the heater bag 22 to be placedinto the tray 142, the interface 144 may be pivoted upwardly out of thetray 142. As is known in the art, the heater tray 142 may heat thedialysate in the heater bag 22 to a suitable temperature, e.g., atemperature appropriate for introduction into the patient. In accordancewith an aspect of the invention, the lid 143 may be closed afterplacement of the heater bag 22 in the tray 142, e.g., to help trap heatto speed the heating process, and/or help prevent touching or othercontact with a relatively warm portion of the heater tray 142, such asits heating surfaces. In one embodiment, the lid 143 may be locked in aclosed position to prevent touching of heated portions of the tray 142,e.g., in the circumstance that portions of the tray 142 are heated totemperatures that may cause burning of the skin. Opening of the lid 143may be prevented, e.g., by a lock, until temperatures under the lid 143are suitably low.

In accordance with another aspect of the invention, the cycler 14includes a user or operator interface 144 that is pivotally mounted tothe cycler 14 housing and may be folded down into the heater tray 142.With the interface 144 folded down, the lid 143 may be closed to concealthe interface 144 and/or prevent contact with the interface 144. Theinterface 144 may be arranged to display information, e.g., in graphicalform, to a user, and receive input from the user, e.g., by using a touchscreen and graphical user interface. The interface 144 may include otherinput devices, such as buttons, dials, knobs, pointing devices, etc.With the set 12 connected, and containers 20 appropriately placed, theuser may interact with the interface 144 and cause the cycler 14 tostart a treatment and/or perform other functions.

However, prior to initiating a dialysis treatment cycle, the cycler 14must at least prime the cassette 24, the patient line 34, heater bag 22,etc., unless the set 12 is provided in a pre-primed condition (e.g., atthe manufacturing facility or otherwise before being put into use withthe cycler 14). Priming may be performed in a variety of ways, such ascontrolling the cassette 24 (namely the pumps and valves) to draw liquidfrom one or more solution containers 20 via a line 30 and pump theliquid through the various pathways of the cassette 24 so as to removeair from the cassette 24. Dialysate may be pumped into the heater bag22, e.g., for heating prior to delivery to the patient. Once thecassette 24 and heater bag line 26 are primed, the cycler 14 may nextprime the patient line 34. In one embodiment, the patient line 34 may beprimed by connecting the line 34 (e.g., by the connector 36) to asuitable port or other connection point on the cycler 14 and causing thecassette 24 to pump liquid into the patient line 34. The port orconnection point on the cycler 14 may be arranged to detect the arrivalof liquid at the end of the patient line (e.g., optically, by conductivesensor, or other), thus detecting that the patient line is primed. Asdiscussed above, different types of sets 12 may have differently sizedpatient lines 34, e.g., adult or pediatric size. In accordance with anaspect of the invention, the cycler 14 may detect the type of cassette24 (or at least the type of patient line 34) and control the cycler 14and cassette 24 accordingly. For example, the cycler 14 may determine avolume of liquid delivered by a pump in the cassette needed to prime thepatient line 34, and based on the volume, determine the size of thepatient line 34. Other techniques may be used, such as recognizing abarcode or other indicator on the cassette 24, patient line 34 or othercomponent that indicates the patient line type.

FIG. 38 shows a perspective view of the inner side of the door 141disconnected from the housing 82 of the cycler 14. This view moreclearly shows how the lines 30 are received in corresponding grooves inthe door 141 and the carriage 146 such that the indicator region 33 iscaptured in a specific slot of the carriage 146. With the indicator atindicator region 33 positioned appropriately when the tubing is mountedto the carriage 146, a reader or other device can identify indicia ofthe indicator, e.g., representing a type of solution in the container 20connected to the line 30, an amount of solution, a date of manufacture,an identity of the manufacturer, and so on. The carriage 146 is mountedon a pair of guides 130 at top and bottom ends of the carriage 146 (onlythe lower guide 130 is shown in FIG. 38). Thus, the carriage 146 canmove left to right on the door 141 along the guides 130. When movingtoward the cassette mounting location 145 (to the right in FIG. 38), thecarriage 146 can move until it contacts stops 131.

FIG. 39 and FIG. 40 show a perspective view of a carriage 146, and anenlarged perspective view of a solution line 30 loaded into the carriage146. In these illustrative embodiments, the carriage 146 may have theability to move on the door 141 along the guide 130. The carriage 146may include five slots 1086, and therefore may have the ability tosupport up to five solution lines 30. Each slot 1086 may include threedifferent sections; a solution line section 1088, an ID section 1090,and a clip 1092. The solution line section 1088 may have a generallycylindrical shaped cavity that allows the solution lines 30 to remainorganized and untangled when loaded into the carriage 146. The clip 1092may be located at the opposite end of each of the slots 1086, relativeto the solution line section 1088. The purpose of the clip 1092 is toprovide a secure housing for a membrane port 1094 located at theconnector end 30 a of the solution line 30, and to prevent the solutionline 30 from moving during treatment.

In one embodiment of the present disclosure, the clip 1092 may have asemicircular shape, and may include a middle region that extendsslightly deeper than the two surrounding edge regions. The purpose ofincluding the deeper middle region is to accommodate a membrane portflange 1096. The flange 1096 may have a substantially greater radiusthan the rest of the membrane port. Therefore, the deeper middle regionis designed to fit the wider flange 1096, while the two edge regionsprovide support so that the membrane port 1094 is immobilized.Additionally, the deep middle region may have two cutouts 1098positioned on opposite sides of the semicircle. The cutouts 1098 mayhave a generally rectangular shape so as to allow a small portion of theflange 1096 to extend into each of the cutouts 1098 when positioned inthe clip 1092. The cutouts 1098 may be formed so that the distancebetween the top edges of each cutout 1098 is slightly less than theradius of the flange 1096. Therefore, a sufficient amount of force isrequired to snap the flange 1096 into the clip 1092. Also, allowing forthe distance between the top edges of the two cutouts 1098 to be lessthan the radius of the flange 1096 helps to keep the solution line 30from inadvertently becoming dislodged during treatment.

In this illustrative embodiment, the carriage 146 may provide superiorperformance over previous designs because of its ability to counteractany deformation of the membrane ports 1094. The carriage 146 is designedto stretch the membrane ports 1094 between the front of the flange 1096and the back of the sleeve. If the membrane port 1094 is furtherstretched at any point during treatment, a wall in the carriage 146 maysupport the flange 1096.

In accordance with another aspect of the present disclosure, the IDsection 1090 may be positioned between the solution line section 1088and the clip 1092. The ID section 1090 may have a generally rectangularshape, thus having the ability to house an identification tag 1100 thatmay snap onto the solution line 30 at the indicator region 33. Theindicator region 33 may have an annular shape that is sized andconfigured to fit within the ID section 1090 when mounted in thecarriage 146. The identification tag 1100 may provide an indication asto the type of solution associated with each line 30, the amount ofsolution, a date of manufacture, and an identity of the manufacturer. Asshown in FIG. 39, the ID section 1090 may include a two dimensional(2-D) barcode 1102, which may be imprinted on the bottom of the IDsection 1090. The barcode 1102 may be a Data Matrix symbol with 10blocks per side, and may include an “empty” Data Matrix code. Thebarcode 1102 may be positioned on the carriage 146 underneath theidentification tag 1100, when the solution lines 30 are loaded into thecarriage 146. However, in an alternative embodiment, the barcode 1102may be added to the ID section 1090 of the carriage 146 by way of asticker or laser engraving. Also, in another embodiment, the barcode1102 may include a Data Matrix that consists of varying dimensions oflength and width, as well as varying numbers of blocks per side.

In this illustrative embodiment, however, the specific number of blocksper side, and the specific length and width of each barcode 1102 wasspecifically chosen in order to provide the most robust design under avariety of conditions. Using only 10 blocks per side may result in thebarcode 1102 having larger blocks, which therefore ensures that thebarcode 1102 is easily readable, even under the dark conditions thatexist inside of the cycler housing 82.

FIG. 41 and FIG. 42 show a perspective view of a foldable identificationtag 1100, and a perspective view of a carriage drive assembly 132including an AutoID camera 1104 mounted to an AutoID camera board 1106respectively. In accordance with an aspect of the present disclosure,the identification tag 1100 may be formed from an injection mold, and itmay then fold to snap around the indicator region 33. The identificationtag 1100 may include edges that are rounded, which may prevent damage tothe solution containers 20 during shipping. The identification tag 1100may also include an 8×8 mm two dimensional (2-D) Data Matrix symbol 1103with 18 blocks per side plus a quiet zone, which may be added by way ofa sticker. The information contained in these Data Matrix symbols 1103may be provided from the camera 1104 to the control system 16, which maythen obtain indicia, through various processes such as by way of imageanalysis. Therefore, the AutoID camera 1104 will have the ability todetect slots 1086 that contain a solution line 30 that is correctlyinstalled, a line 30 that is incorrectly installed, or the absence of aline 30. A solution line 30 that is correctly installed will allow thecamera 1104 to detect the Data Matrix symbol 1103 located on theidentification tag 1100, the absence of a solution line 30 will allowthe camera 1104 to detect an “empty” Data Matrix barcode 1102 located onthe carriage 146 underneath the membrane port 1094, and a solution line30 that is incorrectly loaded will occlude the “empty” Data Matrixbarcode 1102, resulting in no Data Matrix being decoded by the camera1104 for that slot. Thus, the camera 1104 should always decode a DataMatrix in every slot 1086 on the carriage 146, baring an incorrectlyloaded solution line 30.

In this illustrative embodiment, ability to detect features of asolution line 30 by way of an identification tag 1100 located atindicator region 33 may provide benefits such as allowing a user toposition lines 30 in any location of the carriage 146 without having aneffect on system operation. Additionally, since the cycler 14 canautomatically detect solution line features, there is no need to ensurethat specific lines 30 are positioned in particular locations on thecarriage 146 for the system to function properly. Instead, the cycler 14may identify which lines 30 are where, and control the cassette 24 andother system features appropriately.

In accordance with another aspect of the disclosure, the identificationtag 1100 must face into the carriage drive assembly 132 in order to bedecoded by the camera 1104. To ensure this, the solution line receivingstructures on the holder for the solution lines and the identificationtag 1100 may have complementary alignment features. With reference tothe example embodiments of the carriage 146 described herein, thecarriage 146 and identification tag 1100 may have complementaryalignment features. Additionally, the solution lines 30 withidentification tags 1100 should also fit within the Cleanflash machine,thus, the solution line 30 with identification tag 1100 may beconstructed to fit within a 0.53 inch diameter cylinder. In anembodiment, the alignment feature may be a simple flat bottomed bill onthe identification tag 1100 and matching rib in the carriage 146. In oneembodiment of the present disclosure, the bill and rib may slightlyinterfere, forcing the back of the identification tag 1100 in an upwarddirection. While this configuration may create a small amount ofmisalignment, it reduces misalignment in the other axis. Finally, toensure that the identification tag 1100 is properly seated, the front ofthe carriage drive assembly 132 can be designed with only about 0.02inch of clearance over the present carriage 146 and identification tag1100 alignment.

In accordance with another aspect of the disclosure, the AutoID cameraboard 1106 may be mounted to the back of the carriage drive assembly132. Additionally, the AutoID camera 1104 may be mounted to the cameraboard 1106. The camera board 1106 may be placed approximately 4.19inches from the identification tag 1100. However, in an alternativeembodiment, the camera board 1106 may be moved backward without anyserious consequences. A plastic window 1108 may also be attached to thefront of the carriage drive assembly 132, which may allow theidentification tags 1100 to be imaged while also preventing fluid andfinger ingress. The AutoID camera 1104 may include a camera lens, whichmay be any type of lens, such as those used for security applications,or lenses intended for camera phones with the IR filter removed. Inaccordance with an aspect of the present disclosure, the camera lens mayconsist of a small size, light weight, low cost, and high image quality.

Additionally, a single SMD IR LED 1110 may be attached to the cameraboard 1106. The LED 1110 may then illuminate the identification tags1100 so that the camera 1104 may easily decode the Data Matrices 1103.It is important that the identification tags 1100 be illuminated becausethe environment inside of the cycler housing 82 is mostly absent oflight. Therefore, without the LED 1110 to illuminate the identificationtags 1100 the camera 1104 would be unable to decode the Data Matrices1103. Furthermore, to avoid creating glare in front of theidentification tags 1100, the LED 1110 may be mounted 0.75 inch awayfrom the camera 1104. An FPGA may also be mounted to the camera board1106, and may act as an intermediary between the OV3640 image sensor anda cycler's UI processor. In addition to making the processor's jobeasier, this architecture may allow for a different image sensor to beused without a change to any other cycler hardware or software. Finally,image decoding is handled by the open source package libdmtx, which isaddressable from a number of programming languages and can run from acommand line for testing.

In some embodiments, a processor associated with the camera 1104 may becapable of decoding barcodes, data matrices, or the like outside of anindicator region 33 of a solution line installed in a carriage 146. Forexample, a processor associated with camera 1104 may be capable ofdecoding an identifying marking on the packaging or overpack of a set oron the set itself before the set is installed in the cycler. Forexample, during setup, the user interface of a cycler may instruct auser to hold the set packaging in front of or a certain distance awayfrom a window such as window 1108, such that an identifying marking onthe packing is facing the window. In this position, the identifyingmarking will be in the field of the view of the image sensor of thecamera 1104. The camera 1104 may then image the packing and theidentifying marking may be decoded by a processor associated with thecamera 1104. In some embodiments, after the identifying marking has beendecoded, the user interface may prompt the user to confirm variousinformation about the set.

The information encoded in the identifying marking on the set or setpackaging may be the same as or different from that included on theindicator for each solution line. For example, the information on theset packing may be stored for logging purposes (e.g. lot numberidentification etc.). In some embodiments, the information decoded fromthe set packing may be compared to the information included on thesolution lines to ensure that the information matches or corresponds.This may provide for some redundancy allowing the device to double checkthat the lines have been identified correctly and that the correct setwas installed.

FIG. 43 depicts a flowchart detailing a number of example steps whichmay be used to determine information about a set to be installed in acycler by reading an identification marking on the packaging for theset. As shown, in step 5700, a user may be instructed to place a setpackage in front of a camera in the cycler. This may be accomplished viaa prompt generated by a processor of the cycler for display on a userinterface of the cycler. The cycler may then capture an image of theidentification marking on the set packaging or overpack in step 5702. Insome embodiments, the user may be required to interact with the userinterface of the cycler to notify the cycler processor that the setpackaging has been properly positioned. This interaction may generate asignal which is recognized by a processor that then commands the imageto be captured.

In step 5704, a processor of the cycler may decode the identifier on thepackaging. The user may then install the cassette in the cycler in step5706. In some embodiments, before the user installs the cassette, theuser interface of the cycler may display a notification which asks auser to confirm that the set was correctly identified in step 5704. Inone aspect, the cycler may display a message if the packaging isidentified to be for a cassette that would be incompatible with aselected or programmed therapy.

Once the set is installed a camera in the cycler may read one or moreidentifying markings on the set in step 5708. In some embodiments, theidentifying marking read in step 5708 may be an identification tag 1100on each solution line of the set. A processor of the cycler may comparethe information about the set gathered in step 5702 and 5708 to ensurethat the correct set was installed in step 5710. In the event that theinformation does not match, the user may be notified in step 5712.

In some embodiments, to avoid deleterious effects of glare from visiblelight, the data matrices 1103 of the identification tags 1100 mayinclude a fluorescent ink or dye which emits light of a first wavelengthor spectrum in response to absorption of light of a second wavelength orspectrum shone upon it. Such an identification system can be used in anyfluid handling medical device in which fluid containers or bags may havefluids of different compositions, expiration dates, or in whichmanufacturing lot numbers need to be recorded by the device. In anexample embodiment, the system can be used in an automated peritonealdialysis apparatus. The system comprises an image sensor or camera 1104configured to read an image generated by fluorescent light, the imagecomprising a pattern of coded information characterizing the fluid inthe container, the age of the container, its lot number, etc. The fluidline 33 to which the container is attached can be mounted in a mount,cradle or carriage 1088 to fix its location relative to the imagesensor. The fluid line can have an attached identification tag 1100 onor near the mount, onto which a fluorescent identifying marking 1103 hasbeen applied. The marking fluoresces a pattern of light that containsthe coded information upon absorption of light having a non-visiblewavelength emitted by an emitter nearby. The image sensor can beconnected to a controller adapted to receive electronic signals from theimage sensor board 1106 representing the image pattern containing thecoded information.

For example, the data matrices 1103 may include an ink or dye whichfluoresces in the visible spectrum when it absorbs light in theultraviolent spectrum. The data matrices 1103 may be printed with suchan ink or dye and applied to the identification tags 1100 as a sticker,for example Any other suitable means of attaching a data matrix 1103 toan identification tag 1100 may also be used. In addition to an imagesensor, the camera 1104 may include a camera lens which includes afilter that filters out light of the second wavelength or spectrum (e.g.a UV filter). One or more lighting elements, such as LED 1110 (e.g. anSMD LED) that generates light at the second wavelength or spectrum (e.g.UV light) may be attached or connected to the camera board 1106. The LED1110 may then illuminate the data matrices 1103 on the identificationtags 1100. In such embodiments, the data matrices 1103 will emit lightin the first wavelength or spectrum (e.g. in the visible spectrum) inresponse to illumination by light of the second wavelength or spectrum.The camera 1104 may then receive the emitted light of the firstwavelength for decoding of the data matrices 1103. The decoding of thedata matrices 1103 may be accomplished as described above. The effectsof glare from reflected light from the LED may be reduced in thisfashion, since the camera 1104 can be configured to filter out light atthe LED's emitting wavelength/spectrum.

FIG. 44 depicts an illustration of a system in which the identificationtag 1100 has a code printed in a fluorescent material. As shown, one ormore LED's 1110 may illuminate the identification tag 1100 using lightat a wavelength A. The light generated by fluorescence at wavelength Bis received by the camera 1104. As mentioned above, the fluorescence maybe in the visible spectrum and the wavelength emitted by the LED may bea wavelength outside of the visible spectrum such as ultraviolet light.The camera 1104 may optionally include a filter which filters out thewavelength emitted by the LED

Once the identification tags 1100 of each line have been imaged by thecamera 1104 and analyzed, a processor of the cycler may generate ascreen for display on a user interface which displays the results. Thedisplay may indicate various characteristics about the solutionidentified. In other embodiments, the display may disclosecharacteristics of the solutions programmed for use during the therapy,and indicate whether these solutions have been detected by the camera.In an embodiment in which the controller is programmed to perform imagerecognition, and in which the solution line caps are in the field ofview of the image sensor or camera 1104, a results screen may displaywhether the lines were detected in a capped or uncapped state. In theevent that the programmed solutions are not all present or that a lineis uncapped, the controller may be programmed to prevent the user fromproceeding with therapy and to display on a screen the needed correctiveactions. The screen may also optionally display information about thetype of set (e.g. pediatric, adult, extended patient line, etc.)installed in the cycler if such information is collected. Preferably,this action is performed and the screen display is shown prior to theconnection of the solution lines to a cassette so as not to waste anysolution.

FIG. 45 depicts an example of a screen shot 5630 which may be generatedfor display on the user interface of a cycler. The example screen 5630shows the results of identification tag 1100 analysis. In the examplescreen 5630, the characteristics of the solutions programmed for use inthe therapy are shown. These characteristics may include (but are notlimited to): dialysate type or name, concentration of dialysate, volumeof dialysate bag, osmotic agent of the dialysate, other compositioninformation (e.g. buffer information, ionic content information), bagtype, etc. The characteristics shown may differ if the cycler is set upfor at-home use or for use in a dialysis clinic. If there are fewersolution bags programmed for use in the therapy than the maximum allowedfor the cycler, unused solution line or solution line cap locations maybe labeled “none”, “no solution”, or the like.

A number of indicators 5362 may also be included on the example screen5630. These indicators 5632 indicate to a user whether the solution hasbeen identified as installed in the cycler. For example, a checkmark mayappear in an indicator 5632 next to a listed solution type if present.An ‘X’ may appear if the listed item is not detected.

The example screen 5630 shown in FIG. 45 also includes an indicator 5632associated with each solution that indicates whether a cap has beendetected on the installed line. As above, any suitable method may beused to display whether a capped or uncapped line is detected.

In some embodiments, it may be desirable to include a brace, bracemember or stiffener for placement on the distal end of a solution line.It may be configured to surround a portion of the line and/or anattached connector. In any fluid handling apparatus that is configuredto spike the distal end of a fluid line, the distal end preferablyshould be constrained so as not to bend out of alignment with thelongitudinal axis of a hollow spike. In some cases, the distal end ofthe fluid line will have been deformed during manufacture orsterilization. In other cases, the flexibility of the fluid line mayrender it prone to bending as the spiking procedure occurs. A brace maybe rigid and constructed to be mountable over a distal portion of thefluid line, encircling the fluid line at or near the location at whichthe spike penetrates a septum or other barrier in the fluid line. In anembodiment, the brace comprises two rigid half-members arranged tocouple together to encircle the distal end of the fluid line. The bracecan be arranged to form a clamp around the fluid line at this location,the inside features of the clamp configured to mate with complementaryfeatures on the outside surface of the fluid line. Preferably, the bracecan be applied to the fluid line to correct any pre-existing bend in thefluid line, or to prevent the fluid line from bending during operationof the spiking apparatus. Preferably, the outside surface of the bracewhen enclosing the fluid line has a shape, orientation and features thatallow the brace and its enclosed fluid line to be mounted to a fluidline mount, cradle or carriage of the fluid handling apparatus. Aperitoneal dialysis cycler having a fluid line autoconnect apparatus canbe used as an example of such a fluid handling apparatus.

Optionally, an identification tag 1100 may be configured to function asa brace for a solution line. A brace member may serve to surround,constrain or support a portion of the terminal/distal end of thesolution line (or connector) where a solution line septum is located.The brace helps to prevent the surrounded section of the line frombending or deforming out of an orientation dictated by the brace. Abrace may also aid in ensuring a distal end of the line is positionedreliably in its track or cradle on the cycler.

If a solution line is bent or deformed during manufacture, for example,a brace may help to correct this by bending the line back into theproper orientation or geometry. It may, for example, be used to ensurethe end of the solution line remains generally aligned along an axis.This may help to ensure that the end of the line is in a predictableorientation (e.g. coaxial with the longitudinal axis of a correspondingspike on a cassette) and is restricted from bending or deforming when acycler is spiking or otherwise manipulating the line. A brace may alsohelp to prevent a solution line from bending or deforming during heatingwith may occur during sterilization of the line or enclosed solution.

The cycler carriage may be configured to receive and support a bracemember on a solution line. The carriage, in cooperation with a bracemember may then provide further aid in ensuring that the solution lineis in a particular or prescribed orientation and stays in thisorientation as the solution line is spiked or manipulated.

A brace may, for example, be manufactured from any suitable plastic(injection molded or otherwise) of a rigidity sufficient to preventdeformation or bending of the enclosed line or connector. Preferably itis made of a material more heat resistant than the material used to makethe solution line. The edges of a brace are preferably contoured (e.g.blunted or rounded) so as to limit potential for damage of the setduring shipment and handling.

A brace may be constructed in two separate halves that can be joinedtogether around a section of tubing or connector. More conveniently, thetwo portions of a brace can be connected by a living hinge on one side,allowing for greater ease of installation on a solution line orconnector. In embodiments in which the solution line includes a solutionline membrane or septum flange 1096 (see, for example, FIG. 40), theinterior surface of the brace may include a recessed region sized toaccept the flange. The recessed region may be molded to be flanked oneach side by surfaces sized to closely surround the smaller diametersolution line.

As shown in FIG. 46, a solution line 30 is depicted with an examplebrace 5050 being positioned around a segment of the solution line 30 inwhich an interior septum (not shown in FIG. 46) is disposed. In theexample shown, brace 5050 may comprise two halves and include a livinghinge 5052 or thin bridge of material which allows the brace 5050 to befolded into place around the solution line 30. The living hinge 5052 maybe molded as an integral part of the brace 5050. Also as shown in FIG.46, a brace 5050 may include an interior face 5054 which cooperates withfeatures of the outer surface of the solution line 30 so that the brace5050 may fit snuggly around and encompass the solution line 30 and itsexternal features. Thus, when in place around the solution line 30, thebrace 5050 may act to substantially constrain and/or support the portionof the solution line 30 against undesired movement or displacement.

Referring now to FIG. 47, an enlarged view of the example brace 5050depicted in FIG. 46 is shown. As shown in FIG. 47, the brace 5050 hasbeen closed about its living hinge 5052 such that it is nearly in anassembled, ring-like configuration. The brace 5050 may be securedtogether with one or more coupling features. For example, the brace 5050may be snapped together with cooperating snap fit or interference fitfeatures. Alternatively, the coupled portions of a brace 5050 may becoupled together with cooperating friction fit features. In someembodiments, glue or adhesive may be used to join the two halves, or acable tie-like fastening arrangement around the outside surface of thebrace may be used as well. In an example, one side of a brace 5050 mayinclude a toothed projection that engages with a pawl in a receivingstructure on the opposite side of the brace 5050. Thus when the twohalves are coupled together, the coupling features act as a ratchet toprevent a user from removing the brace 5050 from an enclosed line. Thus,any identifying tag present on the brace may not easily be separatedfrom its intended line (and associated solution bag). Any other suitablecoupling arrangement which makes it difficult to separate a brace 5050from its respective line may also be used to accomplish this goal.

In some cases, it may be desirable to allow a user to remove a brace5050 (or an associated identification tag 1100), in which case permanentor semi-permanent coupling features are not included in the constructionof the brace 5050. For example, an appliqué or sticker bearing theidentification marking for the solution line 30 may be used to hold thetwo halves of the brace 5050 around the solution line 30. This may allowa user to easily remove the brace 5050 (or other identification tag1100) from the solution line 30 by tearing or peeling off theidentification marking.

As is shown in FIGS. 46 and 47, the brace 5050 includes a displaysurface 5056 that in some aspects may be substantially flat toaccommodate an identification marking or code when the two halves ofbrace 5050 are coupled together in its assembled configuration. Thisdisplay surface 5056 may serve as a surface to which an identificationmarking may be added (e.g. with a sticker or the like). Theidentification marking may also be molded/etched into or painted ontothe display surface 5056. Thus, the brace 5050 may also act as anidentification tag 1100. A non-flat (e.g., curved) display surface 5056bearing an identification marking may also be used.

As shown, the display surface 5056 in FIGS. 46 and 47 would include aseam since the coupled portions of the brace 5050 couple in the centerregion of the display surface 5056. In alternative embodiments, a brace5050 may be configured such that any seam produced when coupling thebrace 5050 around the solution line 30 would not potentially cause aninterruption of the display surface 5056. This may be desirable as itmay help to ensure that an identification marking added to the displaysurface is not affected by the seam.

In some embodiments, the way in which the two parts of a brace arejoined may provide identifying characteristics, obviating the need foran identification marking. The seam at which the two parts of the braceare joined may have pre-determined geometric patterns or projectionsthat can be detected by an imager in a cycler. Portions of the couplededges of a brace 5050 may be made to project a greater or lesser amountand/or may have different shapes. Braces having different seam patternsmay be assigned to specific types of solution bags. Each solution bagmay have a unique seam pattern.

If desired, the display surface 5056 of brace 5050 can be made to beseamless, as shown in FIGS. 48 and 49. As shown, the brace 5050 isconstructed similarly to that shown in FIGS. 46 and 47 and includes aliving hinge 5052 which allows the brace 5050 to be folded about theouter surface of a solution line 30. The brace 5050 may then be securedin place about the solution line 30 via the interaction of one or morecoupling feature(s) 5053 on the brace 5050. In this case, the displaysurface 5056, intended to bear an identification marking or code,remains a single piece, so that opening the brace does not disrupt thecontinuity of the code or marking. As is best shown in FIG. 49, theexample embodiment includes coupling features 5053 which are cooperatingsnap fit features. One mating face of the brace 5050 includes aprojection with one or more (in this example, two) locking features. Thelocking features may be ramped to aid in guiding the projecting into thereceiving coupling feature 5053 on the opposing mating face of the brace5050. In the example embodiment, the locking features are optionallynon-releasing. That is, there is a substantially vertical catch at theend of the projection. When snapped into the receiving coupling feature,this vertical catch will abut against an interior wall of the receivingfeature making disassociation of the coupling features 5053 difficult.In alternative embodiments, the catch may be angled away from theabutting wall of the receiving element, allowing for disassociation ofthe two components by applying a suitable distracting force on the twocomponents.

The body of the brace 5050 may optionally include additional matingfeatures that are complementary with features on a solution line 30, sothat it can be installed in only one orientation on the solution line30. This may ensure that the display surfaces 5056 of a number of braces5050 on a number of solution lines 30 are oriented substantially alongthe same plane. Including cooperating coupling features on the solutionline 30 and the brace 5050 may help to further retain the brace 5050 ina supporting or bracing position around the solution line 30 as well.

In the example embodiment, and as best shown in FIG. 49, the displaysurface 5056 is formed as a flange-like protrusion or projection thatextends from one half of the ring-like brace 5050 body. The displaysurface 5056, when the brace 5050 is assembled, overhangs a portion ofthe opposite half of the brace 5050 such that the coupling or matingelements of the brace 5050 are joined under the display surface 5056.

As shown, a support surface 5055 for the overhanging portion of thedisplay surface 5056 may be included on the opposite half of the brace5050. This support surface 5055 may help to prevent the flat feature5056 from being bent. The support surface 5055 may be configured toinclude a flat surface or plateau which is in a plane substantiallyparallel to the display surface 5056. A number of standoffs mayalternatively be used. When the brace 5050 is assembled, the supportsurface 5055 is disposed underneath the overhanging portion of thedisplay surface 5056.

Another example of a seamless display surface 5056 of a brace 5050 isdepicted in FIGS. 50 and 51. As shown, the brace 5050 includes a livinghinge 5052 which allows the brace 5050 to be folded about the outersurface of a solution line 30. The brace 5050 may then be secured inplace about the solution line 30 via the interaction of one or morecoupling feature 5053 on the brace 5050. In the example embodiment inFIGS. 50 and 51, the coupling features 5053 are snap fit features. Thebrace 5050 also includes a support surface 5055 which is disposedunderneath the overhanging portion of the display surface 5056 when thebrace 5050 is assembled. In some embodiments, a display surface 5056 ofa brace 5050 may include a raised surface or rim extending along atleast a portion of its perimeter. This may help in positioning of a datamatrix 1103, bar code, QR code, or other identifying marking on thebrace 5050 for situations in which the identifying marking is anappliqué or sticker applied to the brace 5050.

As is best shown in FIG. 51, a brace 5050 may also include one or morealigning or retaining features which allow the brace to properly seat ina holder or cradle on a cycler. For example, a brace 5050 may includeone or more brace-to-carriage coupling features 5057 which cooperatewith complimentary coupling feature(s) in a carriage. Such features mayhelp to retain the brace 5050 and associated solution line 30 in acarriage. Additionally, such features 5057 may help to ensure that thebrace 5050 and solution line 30 are fully seated and properly installedinto the carriage in the proper orientation. In some embodiments, thebrace-to-carriage coupling feature or features 5057 may couple into thecarriage in a snap fit engagement. An audible or tactile click duringseating may signal to the user that the brace 5050 is properlypositioned in the carriage. In the example embodiment, thebrace-to-carriage coupling features 5057 are depicted as cantileveredprojections, although other suitable coupling arrangements may be used.For example, the brace-to-carriage coupling features 5057 may befriction fit or interference fit features. Preferably, the couplingarrangement provides for releasable coupling of the brace 5050 to thecarriage to allow a user to remove solution lines 30 from a carriageeasily.

In some alternative embodiments, one or more fasteners such as a screwmay be used to secure the portions of a brace 5050 around the solutionline 30. In an alternative arrangement, a single piece brace 5050 mayalso be used during the manufacturing of the tubing set.

FIG. 52 depicts a representative longitudinal cross-sectional view ofthe solution line 30, showing a brace 5050 in place around the solutionline 30. Specifically, the brace 5050 is in place around the section ofthe solution line 30 where the septum 30 b is located. Positioning abrace 5050 around this region of the solution line 30 helps to preventdistortions of the solution line 30 during manufacture or sterilizationthat would otherwise cause a misalignment of the septum 30 b with acassette spike when a connection between a cassette and the solutionline 30 is attempted. Additionally, the brace 5050 may preventsignificant bending or deformation of the solution line 30 when beingsubjected to the force from a spike. Thus, including a brace 5050 mayincrease ease of spiking through a septum 30 b when the carriage 146 ofa cycler drives the solution lines 30 onto the spikes of a cassette 24.FIG. 53 depicts an example embodiment of a carriage 146 that includesretaining features 1092 configured to accept a solution line about whicha brace is installed. As shown, the cradles or slots 1086 of thecarriage 146 shown in FIG. 53 do not include an ID section 1090 as shownin FIGS. 39 and 40. In this case, the identifying marking (e.g. a datamatrix 1103) for the set components may be included on each brace.

Referring now also to FIG. 54, a detailed view of region BQ of FIG. 53is shown. The detailed view shown in FIG. 54 depicts an enlarged view oftwo example retaining features 1092 of the carriage 146. As shown, theretaining features 1092 may be sized so as to accept a brace when asolution line is installed in a slot 1086 of the carriage 146. Theretaining features 1092 of the carriage 146 include support featureswhich serve to support a brace during spiking of an installed solutionline. Thus, the retaining features 1092 may ensure that the solutionline is in a desired or prescribed alignment during spiking of thesolution line. The retaining features may comprise clips or clipsections that provide a snap fit between the brace and the cradle orrecess within which it is positioned.

In specific embodiments, the retaining features 1092 include may includeat least one support wall or shoulder which serves as a support featureor member. In the example embodiment shown in FIGS. 53 and 54 a firstsupport wall 5510 a and second support wall 5510 b are included for eachretaining feature 1092. These support walls 5510 a, b are depicted asflanges that can interact with a portion of a brace so as to providesupport for the brace during a spiking operation. For example, eachsupport wall 5510 a, b may abut at least one face of a brace duringspiking. The support walls or shoulders 5510 a, b may also help toproperly locate the solution line in a slot 1086 during installation ofthe line in carriage 146. In some embodiments, a brace may include arecess or groove which is sized to accept a support wall 5510 a, b ofthe carriage 146.

Using the example brace 5050 embodiment shown in FIG. 51, an upstreamface 5512 of the brace 5500 may be supported by the first support wallor shoulder 5510 a when installed in the carriage 146 shown in FIGS. 53and 54. The example brace 5050 in FIG. 51 includes a recessed portion5514. The recessed portion 5514 of the brace 5050 may be sized so thatwhen the brace 5500 is installed in the retaining member or clip 1092,the second support wall 5510 b of the carriage 146 is captured withinthe recess. A downstream face 5516 of the brace 5050 may then besupported by a second support wall or shoulder 5510 b. During spiking ofsolution lines installed in the carriage 146, force will be transmittedfrom the brace 5050 to the carriage 146 through the support walls 5510a, b. Interaction of the brace 5050 and the support walls 5510 a, b ofthe carriage 146 may thus help to constrain the solution line in adesired alignment throughout the spiking of the line.

Also shown in FIG. 54 are a number of optional carriage-to-bracecoupling features 5518. Such features may be included on a carriage 146designed to accept a solution line with a brace 5050. These features5518 may cooperate with one or more features included on a brace 5050such that the brace 5050 is coupled into place and retained in aretaining or clip section 1092 of a slot or cradle 1086. This may helpto keep a solution line from inadvertently becoming dislodged from thecarriage 146. Preferably, an audible or tactile effect is produced whenthe brace couples into carriage-to-brace coupling features 5518. Thismay alert a user that the brace has been fully seated in the retainingor clip section 1092 of a cradle or slot 1086.

In an embodiment, the carriage-to-brace coupling features 5518 areprojections that project into the cradle or slot 1086 such that thewidth of the retaining or clip section 1092 at the location of thefeatures 5518 is reduced to slightly less than that of the brace 5050,requiring some inward deflection of the brace-to-carriage couplingfeatures 5057 before the brace 5050 may snap into the clip section 1092.

In the example embodiment depicted in FIG. 54, the carriage-to-bracecoupling features 5518 can be ramped or stepped. A ramped configurationmay facilitate removal of a brace from the retaining or clip section1092 after a therapy. The height and slope of the ramp is selected topresent a desired degree of resistance when the user is removing a bracefrom a retaining or clip section 1092.

Another example embodiment of a carriage 146 is depicted in FIG. 55. Asshown, the example carriage 146 depicted in FIG. 55 includes a number ofsolution line clips or retaining elements 5520. As shown, a solutionline retaining element 5520 is included in the solution line section1088 of each slot 1086 of the carriage 146. The solution line retainingelements 5520 may act as a receiving structure into which a solutionline may be placed. The solution line retaining elements 5520 help tohold a solution line in place in a slot 1086 on the carriage 146.Additionally, the solution line retaining elements 5520 are configuredto help prevent a solution line from inadvertently becoming dislodgedfrom the carriage 146 or the solution line section 1088 of a slot 1086.The solution line retaining elements 5520 are shown as an integral,continuous part of each solution line section 1088, but in alternateembodiments may be assembled into the carriage 146 as individualcomponents.

In some embodiments, a solution line retaining element 5520 may beconfigured to provide an asymmetrical resistance to dislodgement of acaptured solution line in a track or carriage slot 1086, so that theforce required to dislodge the solution line when pulled from a firstend (e.g., an upstream location) is less than a force required todislodge the solution line if pulled from a second end (e.g. adownstream location) This may help to ensure that a solution line doesnot become accidentally or inadvertently dislodged from the carriage 146or from a track during spiking or during a therapy. Additionally, thisarrangement may allow a user to relatively easily remove a solution linefrom the carriage 146 after a therapy has completed by pulling on afirst (e.g. an upstream) segment of the line. The direction of pullwould generally be at an acute angle with respect to the axis of theslot 1086. Generally, a retaining member 5520 for a flexible tubesegment situated in a track or slot 1086 can comprise a clip having abottom well or channel in which the tube segment may be placed, and atop opening through which the tube segment can be inserted or removed.Inwardly directed projections of the retaining member 5520 near the topof the well help to retain the tube segment and prevent it from slippingout of the top of the retaining member 5520. The captured portion of thetube segment either must be compressed, or the projections distractedapart slightly (e.g., laterally), to allow the tube segment to beremoved using a predetermined force from the retaining member. Ratherthan having a perpendicular orientation to the tube segment, a firstface of the retaining member 5520 can be inclined away from a firstportion of the tube segment as it enters the retaining member 5520. Thismay have the effect of reducing the force required to remove the tubingsegment from the retaining member 5520 when pulling on the firstportion. Thus a user may readily remove the tube segment from theretaining member 5520 by grasping the first portion of the tube segment,whereas a greater force is needed to remove the tube segment if theforce is directed to the second portion of the tube segment on the otherside of the retaining member 5520. Preferably, in a peritoneal dialysiscycler with an autoconnect apparatus, the second portion of the tubesegment receives the cassette spikes, whereas the first portion of thetube segment leads to the solution bags (i.e., is upstream of theretaining member 5520).

Referring now also to FIG. 56, a detailed view of region BS of FIG. 55is shown. The detailed view shown in FIG. 56 depicts an enlarged view ofan example solution line retaining element 5520 included in the carriage146. As shown, the solution line retaining element 5520 projects fromthe walls of the solution line section 1088 inwardly into the slot 1086.In this example, the solution line retaining element 5520 has a “U”-likeshape. When a solution line is clipped into and retained by the solutionline retaining element 5520, the solution line rests on a cradle portion5524 of the element 5520.

As shown, the distance between the sidewalls 5526 of the solution lineretaining element 5520 tapers as the sidewalls 5526 extend toward topface 5522 of the carriage 146. The distance between the sidewalls 5526may be less than the diameter of a solution line at or near the top face5522 of the carriage 146. Alternatively, the sidewalls 5526 may includea step that accomplishes a similar effect.

When a solution line is coupled into a solution line retaining element5520, the user may be required to apply a force sufficient to deform asolution line for it to fit between the sidewalls 5526 at the top of thesolution line retaining element 5520. The degree to which the sidewalls5526 overhang the line determines the amount of force required todislodge the line from the retaining element 5520.

As shown in FIG. 56, a guiding feature, contour or ramp may be includedon either the downstream or upstream face of a solution line retainingelement 5520. In the example embodiment, a guiding feature is shown onthe upstream face of the solution line retaining element 5520. A guidingfeature may serve to allow the solution line to be easily removed. Sucha guiding feature may also facilitate installation of a solution lineinto a solution line clip or retaining feature 5520.

In the example embodiment shown in FIG. 56, the guiding feature is shownas a chamfer or ramp on each sidewall 5526. In other embodiments, aguiding feature may, for example, be a fillet, rounded edge, funnelingfeature, or other contour which is included on each sidewall 5526.

In some embodiments, a physical interference element on the cycler maymake contact with a solution line 30, its connector, its cap, or anassociated brace if it is not properly seated in the carriage 146 whenthe door 141 is closed. Once contacted, this physical interferenceelement may block the travel path of the solution line 30 as the door141 continues to be closed by the user. This physical interferenceelement may, for example, be disposed on or project out of a portion ofthe cycler against which the door is closed. In an embodiment, theinterference element may be positioned so that improperly seatedsolution lines 30 may be pressed into a properly seated position as auser continues to pivot the door 141 toward the closed position. Thephysical interference element may, for example allow for only a smallamount of clearance between itself and properly seated solution lines 30or the carriage 146 when the door 141 is closed. In some embodiments,when the door 141 is in the closed position, the physical interferenceelement may contact and/or compress a portion of a solution line 30, itsconnector, its cap, or an attached brace even if the solution line 30 isproperly seated in the carriage 146. This may provide extra assurancethat the solution line is properly seated in the carriage 146. It willalso prevent a user from being able to fully close the door 141 of thecycler if a solution line 30 is unable to be pressed into a seatedposition on the carriage 146.

FIG. 57 depicts a close up cross-sectional illustration of a portion ofa cycler which includes a carriage 146 and other components which may beoperated to remove cap(s) 31 from solution lines 30, recognize anindicator for each line 30 and fluidly engage the lines 30 with arespective spike on an installed cassette. The door 141 of the cycler isshown in the closed position. As shown, a solution line 30 is in placein the carriage 146 in FIG. 57. The solution line 30 in the exampleembodiment includes a solution line cap 31 which is installed over theconnector end 30 a of the solution line 30. An identification tag 1100is shown in place around a portion of the solution line 30 and a camera1104 is positioned to image the identification tag 1100.

In this example, the solution line cap 31 is in contact with (andoptionally compressed by) a portion of the window 1108 which in FIG. 57serves as the physical interference element. In an embodiment, thesolution line cap 31 is made of an elastomeric material (such assilicone) that is compressible and soft enough to avoid damaging theinterference element (in this case a portion of the window 1108). Withsuch an arrangement, the act of closing the door 141 of the cycler mayensure that a solution line 30 is pressed into a properly seatedposition in the carriage 146. To avoid damaging the interferenceelement, the solution line cap 31 is preferably the first portion of thesolution line 30 to contact or the principle point of contact for thephysical interference element.

If the window 1108 is to provide the physical interference when closingthe door 141, the first or principle point of contact between the window1108 and the solution line 30 is preferably toward the edge of thewindow 1108 or otherwise in the peripheries or out of the field of viewof the camera 1104 behind the window. This may minimize any potentialfor wear or scuffing of the window 1108 in an area which would obscurethe camera's 1104 view of an identification tag 1100.

To further minimize any potential for damage to window 1108, the pointof interference contact may optionally be chamfered 5560. This chamferedfeature 5560 may help to prevent damage to the window when an improperlyseated solution line 30 is forced into a properly seated position as thedoor 141 is closed. The chamfered feature 5560 may also help to preventa solution line 30 from snagging or catching on the window 1108 andcausing the window 1108 to be damaged. As shown, the frame 5562 of thewindow 1108 may also optionally include a chamfer 5564 whose face isoriented substantially parallel to that of the chamfered feature 5560 onthe window 1108. The chamfer 5564 may similarly help to prevent snaggingor catching of a solution line 30 and may also help to prevent damage tothe window 1108. In alternative embodiments, the chamfered feature 5560and/or the chamfer 5564 may be replaced with a rounded feature.

FIG. 58 shows a perspective view of a carriage drive assembly 132 in afirst embodiment that functions to move the carriage 146 to remove thecaps from spikes 160 on the cassette, remove caps 31 on the solutionlines 30 and connect lines 30 to the spikes 160. A drive element 133 isarranged to move left to right along rods 134. In this illustrativeembodiment, an air bladder powers the movement of the drive element 133along the rods 134, but any suitable drive mechanism may be used,including motors, hydraulic systems, etc. The drive element 133 hasforwardly extending tabs 135 that engage with corresponding slots 146 aon the carriage 146 (see FIG. 38, which shows a top slot 146 a on thecarriage 146). Engagement of the tabs 135 with the slots 146 a allowsthe drive element 133 to move the carriage 146 along the guides 130. Thedrive element 133 also includes a window 136, through which an imagingdevice, such as a CCD or CMOS imager, may capture image information ofthe indicators at indicator regions 33 on the lines 30 mounted to thecarriage 146. Image information regarding the indicators at indicatorregions 33 may be provided from the imaging device to the control system16, which may obtain indicia, e.g., by image analysis. The drive element133 can selectively move the cap stripper 149 both to the left and rightalong the rods 134. The cap stripper 149 extends forward and back usinga separate drive mechanism, such as a pneumatic bladder.

FIG. 59 shows a left side perspective view of the carriage driveassembly 132, which more clearly shows how a stripper element of the capstripper 149 is arranged to move in and out (a direction generallyperpendicular to the rods 134) along grooves 149 a in the housing of thecap stripper 149. Each of the semicircular cut outs of the stripperelement may engage a corresponding groove of a cap 31 on a line 30 byextending forwardly when the cap 31 is appropriately positioned in frontof the stripper 149 by the drive element 133 and the carriage 146. Withthe stripper element engaged with the caps 31, the cap stripper 149 maymove with the carriage 146 as the drive element 133 moves. FIG. 60 showsa partial rear view of the carriage drive assembly 132. In thisembodiment, the drive element 133 is moved toward the cassette 24mounting location 145 by a first air bladder 137 which expands to forcethe drive element 133 to move to the right in FIG. 60. The drive elementcan be moved to the left by a second air bladder 138. Alternatively,drive element 133 can be moved back and forth by means of one or moremotors coupled to a linear drive gear assembly, such as a ball screwassembly (in which the carriage drive assembly is attached to a ballnut), or a rack and pinion assembly, for example. The stripper element1491 of the cap stripper 149 can be moved in and out of the cap stripperhousing by a third bladder, or alternatively, by a motor coupled to alinear drive assembly, as described previously.

FIGS. 61-63B show another embodiment of a carriage drive assembly 132and cap stripper 149. As can be seen in the rear view of the carriagedrive assembly 132 in FIG. 61, in this embodiment the drive element 133is moved right and left by a screw drive mechanism 1321. As can be seenin the right rear perspective view of the carriage drive assembly 132 inFIG. 62, the stripper element is moved outwardly and inwardly by an airbladder 139, although other arrangements are possible as describedabove.

FIGS. 63A and 63B show left and right front perspective views of anotherembodiment for the stripper element 1491 of the cap stripper 149. Thestripper element 1491 in the embodiment shown in FIG. 59 included onlyfork-shaped elements arranged to engage with a cap 31 of a solution line30. In the FIG. 63A and 63B embodiment, the stripper element 1491 notonly includes the fork-shaped elements 60, but also rocker arms 61 thatare pivotally mounted to the stripper element 1491. As will be explainedin more detail below, the rocker arms 61 assist in removing spike caps63 from the cassette 24. Each of the rocker arms 61 includes a solutionline cap engagement portion 61 a and a spike cap engagement portion 61b. The rocker arms 61 are normally biased to move so that the spike capengagement portions 61 b are positioned near the stripper element 1491,as shown in the rocker arms 61 in FIG. 63B. However, when a cap 31 isreceived by a corresponding fork-shaped element 60, the solution linecap engagement portion 61 a contacts the cap 31, which causes the rockerarm 61 to pivot so that the spike cap engagement portion 61 b moves awayfrom the stripper element 1491, as shown in FIG. 63A. This positionenables the spike cap engagement portion 61 b to contact a spike cap 63,specifically a flange on the spike cap 63.

FIG. 64 shows a front view of the stripper element 1491 and the locationof several cross-sectional views shown in FIGS. 65-67. FIG. 65 shows therocker arm 61 with no spike cap 63 or solution line cap 31 positionednear the stripper element 1491. The rocker arm 61 is pivotally mountedto the stripper element 1491 at a point approximately midway between thespike cap engagement portion 61 b and the solution cap engagementportion 61 a. As mentioned above, the rocker arm 61 is normally biasedto rotate in a counterclockwise direction as shown in FIG. 65 so thatthe spike cap engagement portion 61 b is positioned near the stripperelement 1491. FIG. 66 shows that the rocker arm 61 maintains thisposition (i.e., with the spike cap engagement portion 61 b located nearthe stripper element 1491) even when the stripper element 1491 advancestoward a spike cap 63 in the absence of a solution line cap 31 engagingwith the fork-shaped element 60. As a result, the rocker arm 61 will notrotate clockwise or engage the spike cap 63 unless a solution line cap31 is present. Thus, a spike cap 63 that does not engage with a solutionline cap 31 will not be removed from the cassette 24.

FIG. 67 shows an example in which a solution line cap 31 is engaged withthe fork-shaped element 60 and contacts the solution line cap engagementportion 61 a of the rocker arm 61. This causes the rocker arm 61 torotate in a clockwise direction (as shown in the figure) and the spikecap engagement portion 61 b to engage with the spike cap 63. In thisembodiment, engagement of the portion 61 b includes positioning theportion 61 b adjacent a second flange 63 a on the spike cap 63 so thatwhen the stripper element 1491 moves to the right (as shown in FIG. 67),the spike cap engagement portion 61 b will contact the second flange 63a and help pull the spike cap 63 from the corresponding spike 160. Notethat the solution line cap 31 is made of a flexible material, such assilicone rubber, to allow a barb 63 c of the spike cap 63 to stretch thehole 31 b of cap 31 (see FIG. 71) and be captured by a circumferentialinner groove or recess within cap 31. A first flange 63 b on the spikecap 63 acts as a stop for the end of solution line cap 31. In anotherexample, the spike cap 63 does not include a first flange 63 b. Thewalls defining the groove or recess in the cap 31 hole 31 b may besymmetrical, or preferably asymmetrically arranged to conform to theshape of the barb 63 c. (See FIG. 84 for a cross sectional view of thecap 31 and the groove or recess.) The second flange 63 a on spike cap 63acts as a tooth with which the spike cap engagement portion 61 b of therocker arm 61 engages in order to provide an additional pulling force todisengage the spike cap 63 from the spike 160, if necessary.

FIG. 68 and FIG. 69 show two different perspective views of anotherembodiment for the stripper element 1491 of the cap stripper 149. Thestripper element 1491 in the embodiment shown in FIG. 59 usesfork-shaped elements 60 arranged to engage with a cap 31 of a solutionline 30. In the embodiment shown in FIG. 68, the stripper element 1491not only includes the fork-shaped elements 60, but may also include aplurality of sensing elements 1112, and a plurality of rocker arms 1114.The sensing elements 1112 and rocker arms 1114 may be arranged in twoparallel columns that run vertically along the stripper element 1491. Inan embodiment, each vertical column may contain five individual sensingelements 1112 and rocker arms 1114, each being positioned to generallyalign in a row corresponding with each of the fork-shaped elements 60.Each sensing element 1112 may be mechanically connected or linked to oneof the corresponding rocker arms 1114. In addition, the assemblycomprising each sensing element 1112 and rocker arm 1114 may include abiasing spring (not shown) that keeps each rocker arm 1114 biased towarda non-engagement position and sensing element 1112 in a position to becontacted and moved by the presence of a solution line cap 31 infork-shaped element 60. Each sensing element 1112 can be displaced andtilted toward the back of the stripper element 1491 by contact with acorresponding solution line cap 31 in forked-shaped element 60. Throughthe mechanical connection between sensing element 1112 and rocker arm1114, rocker arm 1114 can pivotally rotate or tilt laterally towardspike cap 63 upon contact between solution line cap 31 and sensingelement 1112. As rocker arm 1114 rotates or tilts toward spike cap 63,it can engage second flange 63 a on spike cap 63, allowing the stripperassembly to remove spike cap 63 from its corresponding spike.

FIGS. 70A-C illustrate the relationship between sensing element 1112 anda solution line cap 31, and between rocker arm 1114 and spike cap 63.FIG. 70C shows the sensing element 1112 and rocker arm 1114 in theabsence of a spike cap 63 and solution line cap 31. As shown in FIG.70B, an outer flange 31 c of solution line cap 31 has a diametersufficiently large to make contact with sensing element 1112. As shownin FIG. 70A, in the absence of a solution line cap 31, the mere presenceof spike cap 63 alone does not contact sensing element 1112 sufficientlyenough to displace it and cause it to rotate away from spike cap 63. Asshown in FIG. 70B, the displacement of sensing element 1112 causesrotation or tilting of rocker arm 1114 toward spike cap 63, ultimatelyto the point of being positioned adjacent flange 63 a of spike cap 63.As shown in FIG. 70A, when rocker arm 1114 is in a non-deployedposition, it can clear the outer circumference of second flange 63 a ofspike cap 63 by a pre-determined amount (e.g., 0.040 inch). Uponmovement of rocker arm 1114 into a deployed position, its range oftravel may be configured so as to provide a slight compression forceagainst its corresponding spike cap 63 to ensure a secure engagement.

Once a rocker arm 1114 is positioned adjacent flange 63 a of a spike cap63, movement of stripper element 1491 to the right will engage spike cap63 via flange 63 a and help to pull spike cap 63 from its correspondingspike 160. In the absence of a solution line and its associated solutionline cap 31, stripper element 1491 will not remove the correspondingspike cap 63, keeping its associated spike 160 sealed. Thus, fewer thanthe maximum number of cassette spikes 161 may be accessed when fewerthan the maximum number of solution lines need to be used.

FIG. 71 shows a close-up exploded view of the connector end 30 a of asolution line 30 with the cap 31 removed. In FIG. 71, the caps 31 areshown without a finger pull ring like that shown in FIG. 72 for clarity.A pull ring need not be present for operation of the cap 31 with thecycler 14. It may be useful, however, in allowing an operator tomanually remove the cap 31 from the terminal end of solution line 30, ifnecessary. In this illustrative embodiment, the indicator at indicatorregion 33 has an annular shape that is sized and configured to fitwithin a corresponding slot of the carriage 146 when mounted as shown inFIGS. 37 and 38. Of course, the indicator may take any suitable form.The cap 31 is arranged to fit over the extreme distal end of theconnector end 30 a, which has an internal bore, seals, and/or otherfeatures to enable a leak-free connection with a spike 160 on a cassette24. The connector end 30 a may include a pierceable wall or septum (notshown—see FIG. 84 item 30 b) that prevents leakage of solution in theline 30 from the connector end 30 a, even if the cap 31 is removed. Thewall or septum may be pierced by the spike 160 when the connector end 30a is attached to the cassette 24, allowing flow from the line 30 to thecassette 24. As discussed above, the cap 31 may include a groove 31 athat is engaged by a fork-shaped element 60 of the cap stripper 149. Thecap 31 may also include a hole 31 b that is arranged to receive a spikecap 63. The hole 31 b and the cap 31 may be arranged so that, with thecap stripper 149 engaged with the groove 31 a and the spike cap 63 of aspike 160 received in the hole 31 b, the cap 31 may grip the spike cap63 suitably so that when the carriage 146/cap stripper 149 pulls the cap31 away from the cassette 24, the spike cap 63 is removed from the spike160 and is carried by the cap 31. This removal may be assisted by therocker arm 61 engaging with the second flange 63 a or other feature onthe spike cap 63, as described above. Thereafter, the cap 31 and spikecap 63 may be removed from the connector end 30 a and the line 30attached to the spike 160 by the carriage 146.

Solution Line Connector Heater

In one embodiment, a connector heater may be provided near the indicatorregion 33 of the solution lines 30. The connector heater may control thetemperature of the connector end 30 a and in particular the pierceablewall or septum 30 b in order to limit the carriage force required attachthe solution lines to the spikes 160 on the cassette 24. There may beenough variation in ambient (room) temperature to affect the hardness ofthe pierceable wall or septum 30 b of the connector end 30 a of thesolution line, which may in turn affect the performance of the carriage146 in joining the spike 160 to the connector end 30 a of the solutionline 30. For example, at lower ambient temperatures, the increasedhardness of the pierceable wall or septum 30 b may require a greaterforce for spike 160 to penetrate it. On the other hand, at higherambient temperatures, the pierceable wall or septum may be so soft as todeform rather than separate when contacted by the spike 160.

The temperature of the connector ends 30 a may be controlled in a numberof ways, which may include placing a heating element in an appropriatelocation (e.g., at or near location 2807 on the door 141), installing atemperature sensor to monitor the temperature of connector ends 30 a,and using a controller to receive temperature data and modulate theoperation of the heating element. The temperature may be measured by atemperature sensor element mounted on the stripper element 1491 or onthe carriage 146. Alternatively, the temperature of the connector end 30a may be determined using an infra-red (IR) sensor tuned to measuresurface temperature of the connector end 30 a.

The controller may be a software process in the automation computer 300.Alternatively, the controller may be implemented in the hardwareinterface 310. The controller may modulate the power sent to aresistance heater, for example, in one of a number of ways. For example,the controller may send a PWM signal to a MOSFET that can modulate theflow of electrical power to the resistance heater. The controller maycontrol the measured temperature to the desired temperature through anumber of algorithms. One exemplary algorithm includes aproportional-integral (PI) feedback loop on the measured temperature toset the heater power. Alternatively, the heater power can be modulatedin an open loop algorithm that sets the heater power based on themeasured ambient temperature.

In another embodiment, the temperature of the connector end 30 a may becontrolled by mounting a radiant heater in the door 141 at location2807, for example, and aimed at the connector ends. Alternatively, thetemperature of the connector ends may be controlled by mounting athermo-electric element at location 2807, for example, on the door 141.The thermo-electric element may provide either heating or cooling to thearea surrounding the connector ends when mounted on the carriage 146.The radiant heater or thermo-electric element may be modulated by acontroller to maintain the temperature within a given range. Thepreferred temperature range for the connector end 30 a depends on thematerial comprising the pierceable wall or septum, and may be determinedempirically. In one embodiment, the piercable wall is PVC and thepreferred temperature range is set at about 10° C. to 30° C., or morepreferably to a temperature range of about 20° C. to 30° C.

In an embodiment, the connector heater near the indicator region 33 maybe used after the door is closed and before the solution lines 30 areattached to the cassette 24. The automation computer 300 or a controllerenables the connector heater if the measured temperature near theconnector 30 a is outside a preferred range. The automation computer 300or a controller may delay the auto-connection process until the measuredtemperature is within the preferred range. The connector heater may bedisabled after the auto-connection process is completed.

Set Loading and Operation

Once treatment is complete, or the line 30 and/or the cassette 24 areready for removal from cycler 14, the cap 31 and attached spike cap 63may be re-mounted on the spike 160 and the line 30 before the door 141is permitted to be opened and the cassette 24 and line 30 removed fromthe cycler 14. Alternatively, the cassette 24 and solution containerswith lines 30 can be removed en bloc from cycler 14 without re-mountingcap 31 and the attached spike cap 63. An advantage of this approachincludes a simplified removal process, and avoidance of any possiblefluid leaks onto the cycler or surrounding area from improperlyre-mounted or inadequately sealing caps.

FIGS. 72-80 show a perspective view of the carriage 146, cap stripper149 and cassette 24 during a line mounting and automatic connectionoperation. The door 141 and other cycler components are not shown forclarity. In FIG. 72, the carriage 146 is shown in a folded downposition, as if the door 141 is open in the position shown in FIG. 8.The lines 30 and cassette 24 are positioned to be lowered onto the door141. In FIG. 73, the lines 30 are loaded into the carriage 146 and thecassette 24 is loaded into the mounting location 145. At this point thedoor 141 can be closed to ready the cycler for operation. In FIG. 74,the door 141 is closed. Identifiers or indicators located at indicatorregion 33 on the lines 30 may be read to identify various linecharacteristics so that the cycler 14 can determine what solutions, howmuch solution, etc., are loaded. In FIG. 75, the carriage 146 has movedto the left, engaging the caps 31 on the lines 30 with correspondingspike caps 63 on the cassette 24. During the motion, the drive element133 engages the cap stripper 149 and moves the cap stripper 149 to theleft as well. However, the cap stripper 149 remains in a retractedposition. In FIG. 76, the cap stripper 149 moves forward to engage thefork-shaped elements 60 with the caps 31, thereby engaging the caps 31that have been coupled to the spike caps 63. If present, the rocker arms61 may move to an engagement position with respect to the spike caps 63.Next, as shown in FIG. 77, the carriage 146 and the cap stripper 149move to the right, away from the cassette 24 so as to pull the caps 31and spike caps 63 from the corresponding spikes 160 on the cassette 24.It is during this motion that the rocker arms 61, if present, may assistin pulling spike caps 63 from the cassette 24. In FIG. 78, the capstripper 149 has stopped its movement to the right, while the carriage146 continues to move away from the cassette 24. This causes theconnector ends 30 a of the lines 30 to be pulled from the caps 31,leaving the caps 31 and spike caps 63 mounted on the cap stripper 149 byway of the fork-shaped elements 60. In FIG. 79, the cap stripper 149retracts, clearing a path for the carriage 146 to move again toward thecassette 24. In FIG. 80, the carriage 146 moves toward the cassette 24to engage the connector ends 30 a of the lines 30 with the correspondingspikes 160 of the cassette 24. The carriage 146 may remain in thisposition during cycler operation. Once treatment is complete, themovements shown in FIGS. 72-80 may be reversed to recap the spikes 160and the solution lines 30 and remove the cassette 24 and/or lines 30from the cycler 14.

The cycler can be configured to verify that all caps 31 have beenremoved from the cap stripper 149 before any attempt is made to start anew therapy using the cycler. In an embodiment, this may be performedbefore a new cassette and solution line set have been installed in thecycler—either at the end of a therapy or during the startup periodpreceding a new therapy. Alternatively or additionally, a residual capdetection procedure can be performed after the installation of a newcassette and solution line set, but preferably before any cassette spikecaps have been engaged with solution line caps.

The cap detection system comprises a sensor to detect the position ofthe cap stripper relative to a plane in which an installed cassette andset of one or more solution lines reside when mounted in the cycler.Movement of the cap stripper forward or aft (i.e. toward or away fromthe plane) can be monitored by a cycler controller using a positionsensor (e.g., Hall sensor). If a solution line cap/spike cap has notbeen removed from the cap stripper by the user, its presence willinterfere with movement of the cap stripper toward the plane to apre-determined position corresponding to full deployment of the capstripper. The presence of a cap on the cap stripper, interfering withfull deployment of the cap stripper toward the plane can cause thecontroller to issue an alert to the user. If one or more solution lineshave been mounted in the cycler, the interference will likely be betweenthe remaining one or more caps on the cap stripper and the one or morecaps of the solution lines. If no solution lines have been mounted inthe cycler, the controller can command the cap stripper to movelaterally in a direction parallel to the plane to a point at which araised feature of the carriage (e.g., walls 5510 a or 5510 b) providedan interference with any remaining cap in the cap stripper during acommanded movement of the cap stripper toward the plane.

In an embodiment, position sensors for the cap stripper 149 areconfigured to detect the extent of forward deployment of the capstripper toward the carriage when the door 141 is closed. After the door141 is closed (FIG. 74) and before any lateral movement of the carriage146, the cycler controller initiates a forward deployment of the capstripper 149. The position of the cap stripper 149 may be monitored byone or more displacement sensors or by a camera aimed at the appropriatelocation. For example, one or more Hall effect sensors can be configuredto sense a magnet embedded in or attached to the cap stripper 149. Ifone or more cap(s) 31 from a previous mounting operation remain in thecap stripper 149, the leftover cap 31 will be pushed against a newlyinstalled solution line and cap 31 on the carriage 146, preventing thecap stripper 149 from displacing to a fully deployed position. If no newcassette or solution line set have been installed, the cycler controllercan direct the movement of the carriage 146 laterally to apre-determined location that causes one or more features of the carriage146 to act as an interference element against a residual cap 31 on thecap stripper 149, but that allows the cap stripper 149 to fully deployif it is not holding a residual cap 31. In some embodiments, the capstripper 149 may be required to move beyond a predetermined thresholdlocation for the auto-connect process to be allowed to continue. Thepredetermined threshold location may be chosen such that it issufficiently beyond the point at which deployment of the cap stripper149 would be impeded if a leftover cap 31 is present.

The Hall effect sensor may be installed in a location that is protected,separate, partitioned from, or fluidically isolated from the capstripper 149 while still being able to sense a magnet on the capstripper 149.

If the cap stripper 149 is deployed by means of an inflatable bladder,the bladder can optionally not be inflated to maximum pressure whenchecking for leftover caps 31. Instead an inflation pressure need onlybe sufficient to cause to cap stripper 149 to displace toward thecarriage 146, but less than a pressure needed to actually engage asolution line cap installed in the carriage. This pressure may, forexample, be a predetermined pressure; or it may be variable, reaching alevel necessary to move the cap stripper 149. In such embodiments, oncethe position sensor detects movement the controller may either ceasebladder inflation or limit inflation pressure. In some embodiments, thecontroller may require the cap stripper 149 to deploy by a predeterminedamount before the bladder inflation pressure is limited.

In embodiments in which a mechanism other than an inflatable bladder isused to move the cap stripper 149, other devices may be introduced tolimit the force applied by the deployment mechanism during thispre-therapy cap detection test. For example, a torque or pressure sensoror strain gauge may be connected to a gear and motor assembly to feedback similar information to the controller to limit the force applied bythe assembly.

Other position sensors may be used, including but not limited to, anoptical sensor, contact sensor (e.g. microswitch), rangefinding sensor,etc. In other embodiments, the cycler may use sensing elements 1112(see, for example, FIG. 68) to determine if caps 31 are present in thecap stripper 149. A camera can be used to identify a characteristic of acap 31 on the cap stripper 149, such as its shape, color, opacity, lightabsorption or reflection characteristics, etc.

FIG. 81 depicts a flowchart detailing an example of a number of stepsthat may be used to detect the presence of leftover caps 31 in a capstripper 149. The steps shown in FIG. 81 detect the presence of leftovercaps 31 by deploying the cap stripper 149 and monitoring itsdisplacement. Additionally, the flowchart shown in FIG. 81 checks forthe presences of caps 31 in the cap stripper 149 after a set has beeninstalled in the cycler. The test may be performed before and/or after acassette and solution lines have been installed.

As shown, in step 5070, a user may place the solution lines in thecarriage 146 and close the door of the cycler. In step 5072, the cyclermay register that the door of the cycler has been closed. After thecycler registers that the door has been closed, the cycler may deploythe cap stripper 149 toward the carriage 146 in step 5074.

The procedure may be performed before installation of a new cassette andsolution line set. In such an embodiment, the steps 5070 and 5072 maynot be performed. Instead, a step in which the carriage 149 is movedlaterally to a pre-determined position may be performed. Thepredetermined position may be selected such that the carriage 149 actsas an interference element for the cap-bearing cap stripper 149.

The cycler may then check to see if the cap stripper 149 is able todisplace past a predetermined threshold location. In the event that thecap stripper 149 is unable to displace beyond the predeterminedlocation, a user may be notified of the presence of caps 31 left in thecap stripper 149 in step 5076. If the cap stripper 149 is able todisplace beyond the predetermined threshold, a cycler may proceed withlater steps of a solution line connection process in step 5078. In thisstep, the cycler may, for example, connect the cassette spike caps tothe solution line caps installed in the carriage. FIG. 82 depicts anexample screen shot 5590 which may be generated for display on a userinterface of a cycler by a processor of the cycler. The example screen5590 shown in FIG. 82 may for example, be displayed in step 5076 of FIG.81. As shown, the example screen 5590 informs a user that there aresolution line caps present in the cap stripper of the cycler. The screen5590 also includes instructions on how to remove the solution line capsfrom the cap stripper. In the example embodiment, the instructions aretext instructions, though in other embodiments, the instructions mayinclude any combination of text, graphics, and/or animations.

The instructions are divided into a number of steps which may beassociated with user selectable buttons 5592 on the user interface. Forexample, the user interface of the cycler may be a touch screen. A usermay touch, tap, double tap, etc. one of the selectable buttons 5592 onthe screen 5590 to get more detailed instructions on how to perform theassociated step. For example, when the processor of the cycler detectsthat a user has interacted with one of the buttons 5592, the processormay generate a message for display on the screen 5590 with additionaldetail, or may display a new screen with additional information.Alternatively, when the processor of the cycler detects that a user hasinteracted with one of the buttons 5592, the processor may generateanother screen for display that provides additional detail.

The screen 5590 also includes a next button 5594. A user may interactwith the next button 5594 to inform the processor of the cycler that theresidual caps have been removed from the cap stripper. In someembodiments, the cycler may re-check for caps to verify that they havebeen removed from the cap stripper. Optionally, the next button may bedisabled until the cycler processor detects that the door of the cyclerhas been opened and closed.

FIG. 83 depicts an example screen 5600 which may be generated fordisplay on a user interface of a cycler by a processor of the cycler.The example screen 5600 shown in FIG. 83 may for example, be displayedin response to a user interacting with the button 5592 labeled “Removeand discard solution line caps.” in FIG. 82. The example screen 5600includes text describing how the user may complete the step.Additionally, the example screen 5600 includes a graphic 5602 of acycler 14. The graphic 5602 may indicate to a user where the solutionline cap 31 or caps 31 are located. In some embodiments, the screen 5600may optionally include an animation which demonstrates to the user howto remove the solution line caps 31.

To further illustrate the removal of caps 31 and spike caps 63, FIG. 84shows a cross-sectional view of the cassette 24 at five different stagesof line 30 connection. At the top spike 160, the spike cap 63 is stillin place on the spike 160 and the solution line 30 is positioned awayfrom the cassette 24, as in FIG. 74. At the second spike 160 down fromthe top, the solution line 30 and cap 31 are engaged over the spike cap63, as in FIGS. 75 and 76. At this point, the cap stripper 149 mayengage the cap 31 and spike cap 63. At the third spike 160 from the top,the solution line 30, cap 31 and spike cap 63 have moved away from thecassette 24, as in FIG. 77. At this point, the cap stripper 149 may stopmovement to the right. At the fourth spike 160 from the top, thesolution line 30 continues movement to the right, removing the cap 31from the line 30, as in FIG. 78. Once the caps 31 and 63 are retracted,the solution line 30 moves to the left to fluidly connect the connectorend 30 a of the line 30 to the spike 160, as in FIG. 80.

Various sensors can be used to help verify that the carriage 146 and capstripper 149 move fully to their expected positions. In an embodiment,the carriage drive assembly 132 can be equipped with six Hall effectsensors (not shown): four for the carriage 146 and two for the capstripper 149. A first cap stripper sensor may be located to detect whenthe cap stripper 149 is fully retracted. A second cap stripper sensormay be located to detect when the cap stripper 149 is fully extended. Afirst carriage sensor may be located to detect when the carriage 146 isin the “home” position, i.e. in position to permit loading the cassette24 and lines 30. A second carriage sensor may be located to detect whenthe carriage 146 is in position to have engaged the spike caps 63. Athird carriage sensor may be located to detect when the carriage 146 hasreached a position to have removed the caps 31 from the lines 30. Afourth carriage sensor may be located to detect when the carriage 146has moved to a position to have engaged the connector ends 30 a of thelines 30 with the corresponding spikes 160 of the cassette 24. In otherembodiments, a single sensor can be used to detect more than one of thecarriage positions described above. The cap stripper and carriagesensors can provide input signals to an electronic control board(“autoconnect board”), which in turn can communicate specificconfirmation or error codes to the user via the user interface 144.

FIG. 69 shows a perspective view of an alternative embodiment of thecarriage drive assembly 132. The carriage drive assembly 132 in theembodiment shown in FIG. 58 included only the drive element 133, therods 134, the tabs 135 and the window 136. In the FIG. 69 embodiment,the carriage drive assembly 132 not only includes the drive element 133,the rods 134, the tabs 135, and the window 136, but may also include avertical column of AutoID view boxes 1116. The view boxes 1116 may bepositioned directly adjacent to the window 136. Also, the view boxes1116 may be positioned and shaped so that the horizontal axis of each ofthe five slots 1086 located on the carriage 146 run through the centerof a corresponding view box 1116, when the carriage 146 moves eitherright or left along the guides 130. The view boxes 1116 may allow forthe AutoID camera 1104, which is attached to the camera board 1106, todetect if the solution line caps 31 are positioned on the lines 30 priorto the engaging of the solution lines with the spike cap 63.Alternatively, in some embodiments, the individual view boxes may not benecessary. Instead, the window 136 may be enlarged so that the caps 31may be seen through the single window 136. Checking for the solutionline 30 caps 31 may allow for confirmation that the user hasn't removedthe caps 31 prematurely. Once the presence or absence of the caps 31 isdetermined, the camera 1104 can provide a corresponding input signal toan electronic control board (referred to as the autoconnect board laterin the specification), which in turn can communicate specificconfirmation or error codes, relating to the presence of the caps 31 onthe lines 30, to the user via the user interface 144.

In accordance with another aspect of the disclosure, the carriage driveassembly 132 may include an autoconnect board 1118. The autoconnectboard 1118 may be attached to the top of the carriage drive assembly132, and may extend the entire length of the assembly 132. In thisillustrative embodiment, there may also be an LED 1120 mounted to theautoconnect board 1118. The LED 1120 may be located in a fixed positiondirectly above the fork-shaped elements 60. Also, the LED 1120 may bedirected is a fashion so that the light being emitted from the LED 1120travels downward across the stripper element 1491. In accordance withanother aspect of the present disclosure, the carriage drive assembly132 may also include a fluid board 1122. The fluid board 1122 may beattached to the bottom of the carriage drive assembly 132, and may alsoextent the length of the assembly 132. In this illustrative embodiment,there may be a receiver 1124 (not pictured) mounted to the fluid board1122 at a location directly below the LED 1120, which is mounted to theautoconnect board 1118. Therefore, the LED 1120 can emit light acrossthe fork-shaped elements 60, and if the light it detected by thereceiver 1124 then there are no solution line caps 31 left in thestripper element 1491, however, if the light is interrupted on its waytowards the receiver 1124 then there may be a cap 31 left in thestripper element 1491. This LED 1120 and receiver 1124 combinationallows for the detection of caps 31 that may have been inadvertentlyleft in the stripper element 1491 either by the user or by the cycler14. In accordance with an aspect of the disclosure, the fluid board 1122may also have the ability to detect humidity, moisture, or any otherliquid that may be present inside of the carriage drive assembly 132,which could potentially cause the cycler 14 to fail.

There may be an advantage in adjusting the force with which the carriage146 engages the spike caps 63, depending on how many lines 30 are beinginstalled. The force required to complete a connection to the cassette24 increases with the number of caps 31 that must be coupled to spikecaps 63. The sensing device for detecting and reading information fromthe line indicators at indicator regions 33 can also be used to providethe data required to adjust the force applied to drive element 133. Theforce can be generated by a number of devices, including, for example,the first air bladder 137, or a linear actuator such as a motor/ballscrew. An electronic control board (such as, for example, theautoconnect board) can be programmed to receive input from the linedetection sensor(s), and send an appropriate control signal either tothe motor of a linear actuator, or to the pneumatic valve that controlsinflation of air bladder 137. The controller 16 can control the degreeor rate of movement of drive element 133, for example by modulating thevoltage applied to the motor of a linear actuator, or by modulating thepneumatic valve controlling the inflation of bladder 137.

In accordance with an aspect of the present disclosure, it may benecessary for the carriage drive assembly 132 to be capable ofgenerating a force of at least 550 N (124 lbf) on carriage 146, in orderto engage the membrane ports with spikes 160. This force is to bemeasured in the carriage direction of the membrane port spiking onto thecassette 24. The maximum force required to spike a sterilized PVCmembrane port onto the spike 160 may be 110 N. Additionally, the maximumforce required to spike a sterilized JPOC membrane port onto the spike160 may be 110 N. These force requirements ensure carriage driveassembly 132 is able to spike five JPOC ports. In an alternativeembodiment, the PVC port force requirement may be lowered further basedon current insertion forces.

The aspect of the invention by which caps 31 on lines 30 are removedtogether with caps 63 on spikes 160 of the cassette 24 may provide otheradvantages aside from simplicity of operation. For example, since spikecaps 63 are removed by way of their engagement with a cap 31 on a line30, if there is no line 30 mounted at a particular slot on the carriage146, the spike cap 63 at that position will not be removed. For example,although the cassette 24 includes five spikes 160 and correspondingspike caps 63, the cycler 14 can operate with four or less (even no)lines 30 associated with the cycler 14. For those slots on the carriage146 where no line 30 is present, there will be no cap 31, and thus nomechanism by which a spike cap 63 at that position can be removed. Thus,if no line 30 will be connected to a particular spike 160, the cap 63 onthat spike 160 may remain in place during use of the cassette 24. Thismay help prevent leakage at the spike 160 and/or contamination at thespike 160.

The cassette 24 in FIG. 84 includes a few features that are differentfrom those shown, for example, in the embodiment shown in FIGS. 3, 4 and6. In the FIGS. 3, 4 and 6 embodiment, the heater bag port 150, drainline port 152 and patient line port 154 are arranged to have a centraltube 156 and a skirt 158. However, as mentioned above and shown in FIG.84, the ports 150, 152, 154 may include only the central tube 156 and noskirt 158. This is also shown in FIG. 85. The embodiment depicted inFIG. 85 includes raised ribs formed on the outside surface of theleft-side pump chamber 181. The raised ribs may also be provided on theright-side pump chamber 181, and may provide additional contact pointsof the outside walls of pump chambers 181 with the mechanism in the door141 at the cassette mounting location 145, which presses the cassette 24against the control surface 148 when the door 141 is closed. The raisedribs are not required, and instead the pump chambers 181 may have no ribor other features, as shown for the right-side pump chamber 181 in FIG.85. Similarly, the spikes 160 in FIGS. 3, 4 and 6 embodiment include noskirt or similar feature at the base of the spike 160, whereas theembodiment in FIG. 84 includes a skirt 160 a. This is also shown in FIG.85. The skirt 160 a may be arranged to receive the end of the spike cap63 in a recess between the skirt 160 a and the spike 160, helping toform a seal between the spike 160 and the spike cap 63.

Another inventive feature shown in FIG. 84 relates to the arrangement ofthe distal tip of the spike 163 and the lumen 159 through the spike 160.In this aspect, the distal tip of the spike 160 is positioned at or nearthe longitudinal axis of the spike 160, which runs generally along thegeometric center of the spike 160. Positioning the distal tip of thespike 160 at or near the longitudinal axis may help ease alignmenttolerances when engaging the spike 160 with a corresponding solutionline 30 and help the spike 160 puncture a septum or membrane 30 b in theconnector end 30 a of the line 30. As a result, the lumen 159 of thespike 160 is located generally off of the longitudinal axis of the spike160, e.g., near a bottom of the spike 160 as shown in FIG. 84 and asshown in an end view of a spike 160 in FIG. 86. Also, the distal end ofthe spike 160 has a somewhat reduced diameter as compared to moreproximal portions of the spike 160 (in this embodiment, the spike 160actually has a step change in diameter at about ⅔ of the length of thespike 160 from the body 18). The reduced diameter of the spike 160 atthe distal end may provide clearance between the spike 160 and the innerwall of the line 30, thus allowing the septum 30 b a space to fold backto be positioned between the spike 160 and the line 30 when pierced bythe spike 160. The stepped feature 160 b on the spike 160 (shown, e.g.,in FIG. 87) may also be arranged to engage the line 30 at the locationwhere the septum 30 b is connected to the inner wall of the line 30,thus enhancing a seal formed between the line 30 and the spike 160.

In another embodiment, as shown in FIG. 87, the length of the base 160 cof spike 160 may be shortened to reduce the force required to remove thespike cap 63 from spike 160, or to reduce the force required to spikethe connector end 30 a of solution line 30. Shortening the base 160 creduces the area of frictional contact between spike 160 and its cap 63,or between spike 160 and the internal surface of connector end 30 a. Inaddition, the skirt 160 a at the base of spike 160 may be replaced byindividual posts 160 d. The posts 160 d allow the spike cap 63 to beproperly seated onto spike 160 while also allowing for more thoroughcirculation of sterilization fluid or gas around spike 160 during thesterilization process prior to or after packaging of the dialysatedelivery set 12.

To more fully take advantage of the embodiment shown in FIG. 87, a spikecap 64, as shown in FIG. 88 may be used. A skirt 65 on the base of spikecap 64 is constructed to fit snugly over the posts 160 d of the base ofspike 160 shown in FIG. 87. In addition, interrupted ribs 66, 67 withinthe inner circumference of the base of spike 160 may provide a snug fitbetween spike cap 64 and the base 160 c of spike 160, while alsopermitting sterilizing gas or fluid to penetrate more distally over thebase of a capped spike 160. As shown in FIG. 89, in a cross-sectionalview of spike cap 64, a set of three inner ribs 66, 67, 68 may be usedto provide a snug fit between spike cap 64 and the base 160 c of spike160. In an embodiment, rib 66 and rib 67 have interruptions or gaps 66 aand 67 a along their circumference to permit gas or fluid external tothe cassette to flow over the base 160 c of spike 160. A third rib 68may be circumferentially intact in order to make a sealing engagementbetween spike cap 64 and the base 160 c of spike 160, sealing off thebase 160 c from rest of the external surface of spike 160. In otherembodiments, ribs within spike cap 64 may be oriented longitudinallyrather than circumferentially, or in any other orientation to provide asnug fit between spike cap 64 and spike 160, while also permitting anexternal gas or fluid to make contact with the outside of the base 160 cof spike 160. In the embodiment shown, for example, the outer surface ofthe cassette, spike cap and most of the base 160 c of spike 160 can besterilized by exposing the cassette externally to ethylene oxide gas.Because the diameter of the stepped feature 160 b and the distal end ofspike 160 are smaller than the inner diameter of the overlying portionof spike cap 64, any gas or fluid entering the spike lumen from withinthe cassette can reach the outer surface of spike 160 up to the sealingrib 68. Thus any sterilizing gas such as ethylene oxide entering thefluid passages of the cassette 24 may reach the remainder of theexternal surface of spike 160. In an embodiment, the gas may enter thecassette 24 through a vented cap, for example, on the end of patientline 34 or drain line 28.

The spike cap 34 may include 3 or more centering ribs 64D that contactthe end of the spike 160. The ribs 64D are oriented along the majoraccess of spike cap 34 and located near the closed end of the spike cap34. Preferably there are at least three ribs 63D to center the closedend of the cap on the spike without over constraining the cap/spikeorientation. The spike cap 64 includes a tapered end with a blunt tip tofacilitate the penetration of the spike cap 34 into the hole 31 b of thesolution cap 31. The tapered end will guide the spike cap 34 if itmisaligned with the hole 31 b. The blunt tip avoids snagging thesolution cap 31 unlike a sharp tip that might catch the inside edge ofthe hole 31 b and dig into the solution cap material. In contrast ablunt tip can slide past the edges of the hole 31 b. Once the cassette24 and lines 30 are loaded into the cycler 14, the cycler 14 mustcontrol the operation of the cassette 24 to move fluid from the solutionlines 30 to the heater bag 22 and to the patient. FIG. 90 shows a planview of the control surface 148 of the cycler 14 that interacts with thepump chamber side of the cassette 24 (e.g., shown in FIG. 6) to causefluid pumping and flow path control in the cassette 24. When at rest,the control surface 148, which may be described as a type of gasket, andcomprise a sheet of silicone rubber, may be generally flat. Valvecontrol regions 1481 may (or may not) be defined in the control surface148, e.g., by a scoring, groove, rib or other feature in or on the sheetsurface, and be arranged to be movable in a direction generallytransverse to the plane of the sheet. By moving inwardly/outwardly, thevalve control regions 1481 can move associated portions of the membrane15 on the cassette 24 so as to open and close respective valve ports184, 186, 190 and 192 of the cassette 24, and thus control flow in thecassette 24. Two larger regions, pump control regions 1482, may likewisebe movable so as to move associated shaped portions 151 of the membrane15 that cooperate with the pump chambers 181. Like the shaped portions151 of the membrane 15, the pump control regions 1482 may be shaped in away to correspond to the shape of the pump chambers 181 when the controlregions 1482 are extended into the pump chambers 181. In this way, theportion of the control sheet 148 at the pump control regions 1482 neednot necessarily be stretched or otherwise resiliently deformed duringpumping operation.

Each of the regions 1481 and 1482 may have an associated vacuum orevacuation port 1483 that may be used to remove all or substantially allof any air or other fluid that may be present between the membrane 15 ofcassette 24, and the control surface 148 of cycler 14, e.g., after thecassette 24 is loaded into the cycler 14 and the door 141 closed. Thismay help ensure close contact of the membrane 15 with the controlregions 1481 and 1482, and help control the delivery of desired volumeswith pump operation and/or the open/closed state of the various valveports. Note that the vacuum ports 1482 are formed in locations where thecontrol surface 148 will not be pressed into contact with a wall orother relatively rigid feature of the cassette 24. For example, inaccordance with one aspect of the invention, one or both of the pumpchambers of the cassette may include a vacuum vent clearance regionformed adjacent the pump chamber. In this illustrative embodiment asshown in FIGS. 3 and 6, the base member 18 may include vacuum vent portclearance or extension features 182 (e.g., recessed areas that arefluidly connected to the pump chambers) adjacent and outside theoval-shaped depressions forming the pump chambers 181 to allow thevacuum vent port 1483 for the pump control region 1482 to remove any airor fluid from between membrane 15 and control surface 148 (e.g., due torupture of the membrane 15) without obstruction. The extension featuremay also be located within the perimeter of pump chamber 181. However,locating vent port feature 182 outside the perimeter of pump chamber 181may preserve more of the pumping chamber volume for pumping liquids,e.g., allows for the full footprint of pump chamber 181 to be used forpumping dialysate. Preferably, extension feature 182 is located in avertically lower position in relation to pump chamber 181, so that anyliquid that leaks between membrane 15 and control surface 148 is drawnout through vacuum port 1483 at the earliest opportunity. Similarly,vacuum ports 1483 associated with valves 1481 are preferably located ina vertically inferior position with respect to valves 1481.

FIG. 91 shows that control surface 148 may be constructed or molded tohave a rounded transition between the base element 1480 of controlsurface 148 and its valve and pump control regions 1481, 1482. Thejunctions 1491 and 1492 may be molded with a small radius to transitionfrom base element 1480 to valve control region 1481 and pump controlregion 1482, respectively. A rounded or smooth transition helps toprevent premature fatigue and fracture of the material comprisingcontrol surface 148, and may improve its longevity. In this embodiment,channels 1484 leading from vacuum ports 1483 to the pump control regions1482 and valve control regions 1481 may need to be lengthened somewhatto accommodate the transition feature.

The control regions 1481 and 1482 may be moved by controlling apneumatic pressure and/or volume on a side of the control surface 148opposite the cassette 24, e.g., on a back side of the rubber sheet thatforms the control surface 148. For example, as shown in FIG. 92, thecontrol surface 148 may be backed by a mating or pressure delivery block170 that includes control chambers or depressions 171A located inassociation with each control region 1481, and control chambers ordepressions 171B, located in association with each control region 1482,and that are isolated from each other (or at least can be controlledindependently of each other if desired). The surface of mating orpressure delivery block 170 forms a mating interface with cassette 24when cassette 24 is pressed into operative association with controlsurface 148 backed by mating block 170. The control chambers ordepressions of mating block 170 are thus coupled to complementary valveor pumping chambers of cassette 24, sandwiching control regions 1481 and1482 of control surface 148 adjacent to mating block 170, and theassociated regions of membrane 15 (such as shaped portion 151) adjacentto cassette 24. Air or other control fluid may be moved into or out ofthe control chambers or depressions 171A, 171B of mating block 170 forthe regions 1481, 1482, thereby moving the control regions 1481, 1482 asdesired to open/close valve ports of the cassette 24 and/or effectpumping action at the pump chambers 181. In one illustrative embodimentshown in FIG. 92, the control chambers 171A may be arranged ascylindrically-shaped regions backing each of the valve control regions1481. The control chambers or depressions 171B may comprise ellipsoid,ovoid or hemi-spheroid voids or depressions backing the pump controlregions 1482. Fluid control ports 173A may be provided for each controlchamber 171A so that the cycler 14 can control the volume of fluidand/or the pressure of fluid in each of the valve control chambers 1481.Fluid control ports 173C may be provided for each control chamber 171Bso that the cycler 14 can control the volume of fluid and/or thepressure of fluid in each of the volume control chambers 1482. Forexample, the mating block 170 may be mated with a manifold 172 thatincludes various ports, channels, openings, voids and/or other featuresthat communicate with the control chambers 171 and allow suitablepneumatic pressure/vacuum to be applied to the control chambers 171.Although not shown, control of the pneumatic pressure/vacuum may beperformed in any suitable way, such as through the use of controllablevalves, pumps, pressure sensors, accumulators, and so on. Of course, itshould be understood that the control regions 1481, 1482 may be moved inother ways, such as by gravity-based systems, hydraulic systems, and/ormechanical systems (such as by linear motors, etc.), or by a combinationof systems including pneumatic, hydraulic, gravity-based and mechanicalsystems.

FIG. 93 shows an exploded view of an integrated pressure distributionmodule or assembly 2700 for use in a fluid flow control apparatus foroperating a pumping cassette, and suitable for use as pressuredistribution manifold 172 and mating block 170 of cycler 14. FIG. 94shows a view of an integrated module 2700 comprising a pneumaticmanifold or block, ports for supply pressures, pneumatic control valves,pressure sensors, a pressure delivery or mating block and a controlsurface or actuator that includes regions comprising flexible membranesfor actuating pumps and valves on a pumping cassette. The integratedmodule 2700 may also include reference chambers within the pneumaticmanifold for an FMS volume measurement process for determining thevolume of fluid present in a pumping chamber of a pumping cassette. Theintegrated module may also comprise a vacuum port, and a set of pathwaysor channels from interfaces between the actuator and flexible pump andvalve membranes of a pumping cassette to a fluid trap and liquiddetection system. In some embodiments, the pneumatic manifold may beformed as a single block. In other embodiments, the pneumatic manifoldmay be formed from two or more manifold blocks mated together withgaskets positioned between the manifold blocks. The integrated module2700 occupies a relatively small space in a fluid flow controlapparatus, and eliminates the use of tubes or flexible conduitsconnecting the manifold ports with corresponding ports of a pressuredelivery module or block mated to a pumping cassette. Among otherpossible advantages, the integrated module 2700 reduces the size andassembly cost of the pneumatic actuation assembly of a peritonealdialysis cycler, which may result in a smaller and less expensivecycler. Additionally, the short distances between pressure or vacuumdistribution ports on the pressure distribution manifold block andcorresponding pressure or vacuum delivery ports on a mating pressuredelivery block, together with the rigidity of the conduits connectingthe ports, may improve the responsiveness of an attached pumpingcassette and the accuracy of cassette pump volume measurement processes.When used in a peritoneal dialysis cycler 14, in an embodiment, anintegrated module comprising a metallic pressure distribution manifoldmated directly to a metallic pressure delivery block may also reduce anytemperature differences between the control volume 171B and thereference chamber 174 of the cycler 14, which may improve the accuracyof the pump volume measurement process.

An exploded view of the integrated module 2700 is presented in FIG. 93.The actuator surface, mounted on a mating block or pressure deliveryblock, is analogous or equivalent to the gasket or control surface 148,that includes flexible regions arranged to move back and forth to pumpfluid and/or open and close valves by pushing or pulling on a membrane15 of a pump cassette 24. With respect to cycler 14, the control surface148 is actuated by the positive and negative pneumatic pressure suppliedto the control volumes 171A, 171B behind the control regions 1481, 1482.The control surface 148 attaches to the pressure delivery block ormating block 170 by fitting tightly on a raised surface 2744 on thefront surface of the mating block 170 with a lip 2742. The mating block170 may include one or more surface depressions 2746 to align with andsupport the oval curved shape of one or more corresponding pump controlsurfaces 1482, forming a pump control chamber. A similar arrangement,with or without a surface depression, may be included in forming a valvecontrol region 171A to align with a corresponding control surface 1481for controlling one or more valves of a pumping cassette. The matingblock 170 may further include grooves 2748 on the surface of depression2746 of mating block 170 behind the pump control surface 1482 tofacilitate the flow of control fluid or gas from the port 173C to theentire back surface the pump control surface 1482. Alternatively, ratherthan having grooves 2748, the depression 2746 may be formed with aroughened surface or a tangentially porous surface.

The mating block 170 connects the pressure distribution manifold 172 tothe control surface 148, and delivers pressure or vacuum to variouscontrol regions on control surface 148. The mating block 170 may also bereferred to as a pressure delivery block in that it provides pneumaticconduits to supply pressure and vacuum to the valve control regions 1481and the pump control regions 1482, vacuum to the vacuum ports 1483 andconnections from the pump control volumes 171B to the pressure sensors.The ports 173A connect the valve control volumes 171A to the pressuredistribution manifold 172. The ports 173C connect the pump controlvolume 171B to the pressure distribution manifold 172. The vacuum ports1483 are connected to the pressure distribution manifold 172 via ports173B. In one embodiment, the ports 173B extend above the surface of thepressure delivery block 170 to pass through the control surface 148 toprovide vacuum at port 1483 without pulling the control surface 148 ontothe port 173B and blocking flow.

The pressure delivery block 170 is attached to the front face of thepressure distribution manifold 172. The ports 173A, 173B, 173C line upwith pneumatic circuits on the pressure distribution manifold 172 thatconnect to valve ports 2714. In one example, the pressure delivery block170 is mated to the pressure distribution manifold 172 with a front flatgasket 2703 clamped between them. The block 170 and manifold 172 areheld together mechanically, which in an embodiment is through the use ofbolts 2736 or other types of fasteners. In another example, rather thana flat gasket 2703, compliant elements are placed in or molded in eitherthe pressure delivery block 170 or the pressure distribution manifold172. Alternatively, the pressure delivery block 170 may be bonded to thepressure distribution manifold 172 by an adhesive, double sided tape,friction welding, laser welding, or other bonding method. The block 170and manifold 172 may be formed of metal or plastic and the bondingmethods will vary depending on the material.

The pressure distribution manifold 172 contains ports for the pneumaticvalves 2710, reference chambers 174, a fluid trap 1722 and pneumaticcircuitry or of the integrated module 2700 connections providespneumatic connections between the pressure reservoirs, valves, andcontains ports 2714 that receive multiple cartridge valves 2710. Thecartridge valves 2710 include but are not limited to the binary valves2660 controlling flow to valve control volumes 171A, the binary valvesX1A, X1B, X2, X3 controlling flow to pump control volumes 171B, and thebinary valves 2661-2667 controlling flow to the bladders 2630, 2640,2650 and pressure reservoirs 2610, 2620. The cartridge valves 2710 arepressed into the valve ports 2714 and electrically connected to thehardware interface 310 via circuit board 2712.

The pneumatic circuitry in the pressure distribution manifold 172 may beformed with a combination of grooves or slots 1721 on the front and backfaces and approximately perpendicular holes that connect the grooves1721 on one face to valve ports 2714, the fluid trap 1722 and to groovesand ports on the opposite face. Some grooves 1721 may connect directlyto the reference chambers 174. A single perpendicular hole may connect agroove 1721 to multiple valve ports 174 that are closely spaced andstaggered. Sealed pneumatic conduits are formed when the grooves 1721are isolated from one another by, in one example, the front flat gasket2703 as shown in FIG. 93.

The presence of liquid in the fluid trap 1722 may be detected by a pairof conductivity probes 2732. The conductivity probes 2732 slide througha back gasket 2704, a back plate 2730 and holes 2750 before entering thefluid trap 1722 in the pressure distribution manifold 172.

The back plate 2730 seals the reference volumes 174, the grooves 1721 onthe back face of the pressure distribution manifold 172 and providesports for the pressure sensors 2740 and ports for pressure and vacuumlines 2734 and vents to the atmosphere 2732. In one example, thepressure sensors may be IC chips soldered to a single board 2740 andpressed as a group against the back gasket 2704 on the back plate 2730.In one example, bolts 2736 clamp the back plate 2730, pressuredistribution manifold 172 and pressure delivery block 170 together withgaskets 2703, 2702 between them. In another example, the back plate 2730may be bonded to the pressure delivery manifold 172 as described above.The assembled integrated module 2700 is presented in FIG. 95.

FIG. 95 presents a schematic of the pneumatic circuit in the integratedmanifold 2700 and pneumatic elements outside the manifold. The pump 2600produces vacuum and pressure. The pump 2600 is connected via 3 wayvalves 2664 and 2665 to a vent 2680 and the negative or vacuum reservoir2610 and the positive reservoir 2620. The pressure in the positive andnegative reservoirs 2620, 2610 are measured respectively by pressuresensors 2678, 2676. The hardware interface 310 controls the speed of thepump 2600 and the position of 3-way valves 2664, 2665, 2666 to controlthe pressure in each reservoir. The auto-connect stripper elementbladder 2630 is connected via 3-way valve 2661 to either the positivepressure line 2622 or the negative or vacuum line 2612. The automationcomputer 300 commands the position of valve 2661 to control the locationof the stripper element 1461. The occluder bladder 2640 and pistonbladder 2650 are connected via 3-way valves 2662 and 2663 to either thepressure line 2622 or vent 2680. The automation computer 300 commandsvalve 2663 to connect the piston bladder 2650 to the pressure line 2622after the door 141 is closed to securely engage the cassette 24 againstthe control surface 148. The occluder bladder 2640 is connected to thepressure line 2622 via valve 2662 and restriction 2682. The occluderbladder 2640 is connected to the vent 2680 via valve 2662. The orifice2682 advantageously slows the filling of the occluder bladder 2640 thatretracts the occluder 147 in order to maintain the pressure in thepressure line 2622. The high pressure in the pressure line 2622 keepsthe various valve control surfaces 171A and the piston bladder 2650actuated against the cassette 24, which prevents flow to or from thepatient as the occluder 147 opens. Conversely the connection from theoccluder bladder 2640 to the vent 2680 is unrestricted, so that occluder147 can quickly close.

The valve control surfaces 1481 are controlled by the pressure in thevalve control volume 171A, which in turn is controlled by the positionof the 3-way valves 2660. The valves 2660 can be controlled individuallyvia commands from the automation computer 300 passed to the hardwareinterface 310. The valves controlling the pumping pressures in the pumpcontrol volumes 171B are controlled with 2-way valves X1A, X1B. Thevalves X1A, X1B in one example may be controlled by the hardwareinterface 310 to achieve a pressure commanded by the automation computer300. The pressure in each pump control chamber 171B is measured bysensors 2672. The pressure in the reference chambers is measured bysensors 2670. The 2-way valves X2, X3 respectively connect the referencechamber 174 to the pump control chamber 171B and the vent 2680.

The fluid trap 1722 is to the vacuum line 2612 during operation asexplained elsewhere in this application. The fluid trap 1722 isconnected by several lines to the ports 173B in the pressure deliveryblock 170. The pressure in the fluid trap 1722 is monitored by pressuresensor 2674 that is mounted on the back plate 2730.

The vacuum ports 1483 may be employed to separate the membrane 15 fromthe control surface 148 at the end of therapy before or during theopening the door. The vacuum provided by the negative pressure source tothe vacuum ports 1483 sealingly engages the membrane 15 to the controlsurface 148 during therapy. In some instances a substantial amount offorce may be needed to separate the control surface from the cassettemembrane 15, preventing the door 141 from freely rotating into the openposition, even when the application of vacuum is discontinued. Thus, inan embodiment, the pressure distribution module 2700 is configured toprovide a valved channel between the positive pressure source and thevacuum ports 1483. Supplying positive pressure at the vacuum ports 1483may aid in separating the membrane 15 from the control surface 148,thereby allowing the cassette 24 to separate more easily from thecontrol surface 148 and allow the door 141 to open freely. The pneumaticvalves in the cycler may be controlled by the automation computer 300 toprovide a positive pressure to the vacuum ports 1483. The manifold 172may include a separately valved channel dedicated for this purpose, oralternatively it may employ the existing channel configurations andvalves, operated in a particular sequence.

In one example the vacuum ports 1483 may be supplied with positivepressure by temporarily connecting the vacuum ports 1483 to the positivepressure reservoir 2620. The vacuum ports 1483 are normally connected tothe vacuum reservoir 2610 via a common fluid collection chamber or fluidtrap 1722 in the manifold 172 during therapy. In one example, thecontroller or automation computer may open valve X1B between thepositive pressure reservoir and the volume control chamber 171B and thevalve X1A between the negative pressure reservoir and the same volumecontrol chamber 171B simultaneously, which will pressurize the air inthe fluid trap 1722 and the vacuum ports 1483. The pressurized air willflow through the vacuum ports 1483 and between the membrane 15 and thecontrol surface 148, breaking any vacuum bond between the membrane andcontrol surface. However, in the illustrated manifold, the stripperelement 1491 of the cap stripper 149 may extend while the positivepressure is supplied to common fluid collection chamber 1722 fluid,because the stripper bladder 2630 is connected to a the vacuum supplyline 2612. In this example, in a subsequent step, the fluid trap 1722may be valved off from the now-pressurized vacuum line and the twovalves X1A, X1B connecting the positive and vacuum reservoirs to thevolume control chamber 171B may be closed. The vacuum pump 2600 is thenoperated to reduce the pressure in the vacuum reservoir 2610 and thevacuum supply line 2612, which in turn allows the stripper element 1491to be withdrawn. The door 141 may then be opened after detaching thecassette 24 from the control surface 148 and retracting the stripperelement 1491.

In accordance with an aspect of the disclosure, the vacuum ports 1483may be used to detect leaks in the membrane 15, e.g., a liquid sensor ina conduit or chamber connected to a vacuum port 1483 may detect liquidif the membrane 15 is perforated or liquid otherwise is introducedbetween the membrane 15 and the control surface 148. For example, vacuumports 1483 may align with and be sealingly associated with complementaryvacuum ports 173B in mating block 170, which in turn may be sealinglyassociated with fluid passages 1721 leading to a common fluid collectionchamber 1722 in manifold 172. The fluid collection chamber 1722 maycontain an inlet through which vacuum can be applied and distributed toall vacuum ports 1483 of control surface 148. By applying vacuum to thefluid collection chamber 1722, fluid may be drawn from each of thevacuum ports 173B and 1483, thus removing fluid from any space betweenthe membrane 15 and the control surface 148 at the various controlregions. However, if there is liquid present at one or more of theregions, the associated vacuum port 1483 may draw the liquid into thevacuum ports 173B and into the lines 1721 leading to the fluidcollection chamber 1722. Any such liquid may collect in the fluidcollection chamber 1722, and be detected by one or more suitablesensors, e.g., a pair of conductivity sensors that detect a change inconductivity in the chamber 1722 indicating the presence of liquid. Inthis embodiment, the sensors may be located at a bottom side of thefluid collection chamber 1722, while a vacuum source connects to thechamber 1722 at an upper end of the chamber 1722. Therefore, if liquidis drawn into the fluid collection chamber 1722, the liquid may bedetected before the liquid level reaches the vacuum source. Optionally,a hydrophobic filter, valve or other component may be placed at thevacuum source connection point into the chamber 1722 to help furtherresist the entry of liquid into the vacuum source. In this way, a liquidleak may be detected and acted upon by controller 16 (e.g., generatingan alert, closing liquid inlet valves and ceasing pumping operations)before the vacuum source valve is placed at risk of being contaminatedby the liquid.

In the example schematic shown in FIG. 95, a calibration port 2684 isdepicted. The calibration port 2684 may be used to calibrate the variouspressure sensors 2670, 2672, 2674, 2676, 2677, 2678 in the pneumaticsystem. For example, a pressure reference may be connected to thepneumatic circuit of the cycler via the calibration port 2684. With thepressure reference connected, the valves of the pneumatic system may beactuated so as to connect all of the pressure sensors 2670, 2672, 2674,2676, 2677, 2678 to the same fluid volume. A known pressure may then beestablished in the pneumatic system using the pressure reference. Thepressure readings from each of the pressure sensors 2670, 2672, 2674,2676, 2677, 2678 may be compared to the known pressure of the pressurereference and the pressure sensors 2670, 2672, 2674, 2676, 2677, 2678may then be calibrated accordingly. In some embodiments, selectedpressure sensors of the pressure sensors 2672, 2674, 2676, 2677, 2678may be connected and brought to the pressure of the reference forcalibration in groups or individually.

Any fluid handling device (i.e. base unit) that is configured to actuatediaphragm-based pumps and valves on a removable cassette can takeadvantage of its pneumatic (or hydraulic) cassette interface to receivea calibrating reference pressure via a specialized calibrating cassette(or ‘cassette fixture’). A calibrating cassette can have the sameoverall dimensions as a standard fluid pumping cassette, so that it canprovide a sealing interface with the cassette interface or controlsurface of the base unit. One or more of the pump or valve regions canbe allowed to communicate with a corresponding region of the interfaceto which it mates, so that a reference pneumatic or hydraulic pressurecan be introduced through the calibrating cassette and into thepneumatic or hydraulic flow paths of the base unit (e.g. via a pneumaticor hydraulic manifold).

For example, in a pneumatically operated peritoneal dialysis cycler, thepneumatic circuitry of the cycler may be accessed directly through thecassette interface of the cycler. This may for example, be accomplishedusing a modified cassette or cassette fixture which allows the controlsurface 148 to create a seal against the cassette fixture. Additionally,the cassette fixture may be constructed to include at least one accessport in fluid communication with a vacuum port 173B of the cassetteinterface. In the absence of a vacuum port (e.g. in embodiments havingslits or perforations in the control surface) the access port mayinstead be placed in communication with the vacuum vent feature of thecassette interface or control surface.

The cassette fixture (or calibrating cassette) may be constructed tohave a direct flow path from an external cassette port to the accessport facing the device interface, the external cassette port then beingavailable for connection to a pressure reference. As described above,all or some of the pressure sensors 2670, 2672, 2674, 2676, 2677, 2678may be placed into fluid communication with a common volume, through theappropriate actuation of pneumatic control valves in the pressuredistribution manifold. A known pressure may be established in thatvolume using the pressure reference. The pressure readings from each ofthe pressure sensors 2670, 2672, 2674, 2676, 2677, 2678 may be comparedto the known pressure of the pressure reference and the pressure sensors2670, 2672, 2674, 2676, 2677, 2678 may then be calibrated accordingly.

In some embodiments of a pressure distribution manifold, it may not bepossible for all of the pressure sensors 2670, 2672, 2674, 2676, 2677,2678 to be connected to a common volume at one time. In that case, theflow paths to the individual pressure sensors 2670, 2672, 2674, 2676,2677, 2678 may need to be opened in a sequential manner to ensurecalibration of all sensors. Additionally, it should be noted that oncecalibrated, one or more of the pressure sensors 2670, 2672, 2674, 2676,2677, 2678 may be used to calibrate other pressure sensors 2670, 2672,2674, 2676, 2677, 2678 in a pressure distribution manifold of a baseunit or cycler. The previously calibrated pressure sensor or sensors maybe placed into a common volume with the uncalibrated pressure sensor(e.g. via suitable valve actuations). The pressure of the common volumemay be known via the calibrated pressure sensor(s). The uncalibratedpressure sensor's reading may be compared to the known pressure of thecommon volume and then calibrated accordingly.

FIG. 96 depicts a schematized view of an embodiment of a cassettefixture 4570. As shown, the cassette fixture 4570 has the same outlineas a standard pump cassette 24 described earlier. The cassette fixture4570 includes an access port 4572 associated with a specific valve orpump region of a standard cassette to align with its correspondingregion on the cassette interface (control surface) of the base unit. Thecassette fixture 4570 otherwise can have a flat smooth interface surfaceto allow the control surface to seal against it when it is mated to thebase unit or cycler. Preferably, the cassette fixture 4570 is formedfrom a metal or other hard, stiff material. A resistance to flexing ordeformation under pressure may help to increase reliability andconsistency over multiple calibrations of multiple cyclers. As shown,the cassette fixture 4570 includes an access port 4572 which is recessedinto the face of the cassette fixture 4570. The access port 4572communicates with a fluid path 4573 extending to tubing 4574 leadingaway from the cassette fixture 4570. A cassette port or fitting may beincluded on the side of the cassette for connection via tubing to areference pressure source 4576 in the example embodiment.

FIGS. 97 and 98 depict other representations of a cassette fixture 4570adapted from a modified cassette such as the cassette 24 shown in FIG.3. In such examples, the cassette fixture 4570 may be made by removingor not including the sheeting or membrane from the control side of thecassette which faces a control surface or cassette interface 148 (see,for example, FIG. 90) of a cycler when installed in the cycler.Referring to FIG. 3, for example, the membrane 15 may not be included onthe cassette 24. Thus, the pneumatic circuit of the cycler may beaccessed directly through the cassette 24. Alternatively, the membraneor sheeting may be interrupted (e.g. removed, perforated, slit, or thelike) on only a portion of the cassette to create the cassette fixture4570. For example, the membrane may be modified in this manner in thearea over which an access port 4572 of the cassette fixture 4570 islocated.

Additionally, tubing 4574 may be attached to one or more of the externalconnection sites of a standard cassette to create the necessary fluidcommunication path of a cassette fixture 4570. The external connectionsites can include any tubing attachment sites on the standard cassette,or may comprise more robust fittings for repeated use in calibrationprocedures. Referring to FIG. 3, external connection sites may includethe cassette spikes 160 and/or the ports 150, 152 and 154. The cassettemay then be modified so that all other external connection sites may beblocked, plugged or otherwise sealed.

As above, the tubing 4574 leads from a fluid flowpath 4573 fluidicallyconnected to an access port 4572 in the cassette fixture 4570 to providea connection path to a pressure reference 4576. The access port 4572 maybe a pre-existing opening or valve port in the cassette body.Additionally, the fluid path 4573 may be any pre-existing pathway orcombination of pathways in the cassette body which allow fluidcommunication from the access port 4572 to the tubing 4574 or anassociated fitting on the side of the cassette. For example, a fluidpath 4573 may include one or more valve port, valve well, pump chamber,and/or channel in the cassette body or any combination thereof.

In one embodiment, the inner wall of the control chambers 171B caninclude raised elements somewhat analogous to the spacer elements 50 ofthe pump chamber, e.g., as shown in FIG. 92 for the control chambers171B associated with the pump control regions 1482. These raisedelements can take the form of plateau features, ribs, or otherprotrusions that keep the control ports recessed away from the fullyretracted control regions 1482. This arrangement may allow for a moreuniform distribution of pressure or vacuum in the control chamber 171B,and prevent premature blocking of any control port by the controlsurface 148. A pre-formed control surface 148 (at least in the pumpcontrol regions) may not be under a significant stretching force whenfully extended against either the inner wall of the pump chamber of thecassette 24 during a delivery stroke, or the inner wall of the controlchamber 171 during a fill stroke. It may therefore be possible for thecontrol region 1482 to extend asymmetrically into the control chamber171B, causing the control region 1482 to prematurely close off one ormore ports of the control chamber before the chamber is fully evacuated.Having features on the inner surface of the control chamber 171B thatprevent contact between the control region 1482 and the control portsmay help to assure that the control region 1482 can make uniform contactwith the control chamber inner wall during a fill stroke.

As suggested above, the cycler 14 may include a control system 16 with adata processor in electrical communication with the various valves,pressure sensors, motors, etc., of the system and is preferablyconfigured to control such components according to a desired operatingsequence or protocol. The control system 16 may include appropriatecircuitry, programming, computer memory, electrical connections, and/orother components to perform a specified task. The system may includepumps, tanks, manifolds, valves or other components to generate desiredair or other fluid pressure (whether positive pressure—above atmosphericpressure or some other reference—or negative pressure or vacuum—belowatmospheric pressure or some other reference) to control operation ofthe regions of the control surface 148, and other pneumatically-operatedcomponents. Further details regarding the control system 16 (or at leastportions of it) are provided below.

In one illustrative embodiment, the pressure in the pump controlchambers 171B may be controlled by a binary valve, e.g., which opens toexpose the control chamber 171 to a suitable pressure/vacuum and closesto cut off the pressure/vacuum source. The binary valve may becontrolled using a saw tooth-shaped control signal which may bemodulated to control pressure in the pump control chamber 171B. Forexample, during a pump delivery stroke (i.e., in which positive pressureis introduced into the pump control chamber 171B to move the membrane15/control surface 148 and force liquid out of the pump chamber 181),the binary valve may be driven by the saw tooth signal so as to open andclose at a relatively rapid rate to establish a suitable pressure in thecontrol chamber 171B (e.g., a pressure between about 70-90 mmHg). If thepressure in the control chamber 171B rises above about 90 mmHg, the sawtooth signal may be adjusted to close the binary valve for a moreextended period. If the pressure drops below about 70 mmHg in thecontrol chamber 171B, the saw tooth control signal may again be appliedto the binary valve to raise the pressure in the control chamber 171.Thus, during a typical pump operation, the binary valve will be openedand closed multiple times, and may be closed for one or more extendedperiods, so that the pressure at which the liquid is forced from thepump chamber 181 is maintained at a desired level or range (e.g., about70-90 mmHg).

In some embodiments and in accordance with an aspect of the disclosure,it may be useful to detect an “end of stroke” of the membrane 15/pumpcontrol region 1482, e.g., when the membrane 15 contacts the spacers 50in the pump chamber 181 or the pump control region 1482 contacts thewall of the pump control chamber 171B. For example, during a pumpingoperation, detection of the “end of stroke” may indicate that themembrane 15/pump control region 1482 movement should be reversed toinitiate a new pump cycle (to fill the pump chamber 181 or drive fluidfrom the pump chamber 181). In one illustrative embodiment in which thepressure in the control chamber 171B for a pump is controlled by abinary valve driven by a saw tooth control signal, the pressure in thepump chamber 181 will fluctuate at a relatively high frequency, e.g., afrequency at or near the frequency at which the binary valve is openedand closed. A pressure sensor in the control chamber 171B may detectthis fluctuation, which generally has a higher amplitude when themembrane 15/pump control region 1482 are not in contact with the innerwall of the pump chamber 181 or the wall of the pump control chamber171B. However, once the membrane 15/pump control region 1482 contactsthe inner wall of the pump chamber 181 or the wall of the pump controlchamber 171B (i.e., the “end of stroke”), the pressure fluctuation isgenerally damped or otherwise changes in a way that is detectable by thepressure sensor in the pump control chamber 171B. This change inpressure fluctuation can be used to identify the end of stroke, and thepump and other components of the cassette 24 and/or cycler 14 may becontrolled accordingly.

In one embodiment, the pneumatic pressure applied to the control chamber171B is actively controlled by a processor receiving a signal from apressure transducer 2672 (FIG. 37C) connected to the control chamber171B and a fast acting binary valve X1A, X1B between a pressurereservoir 2620, 2610 and the control chamber 171B. The processor maycontrol the pressure with a variety of control algorithms includingclosed loop proportional or proportional-integrator feedback controlthat varies the valve duty cycle to achieve the desired pressure in thecontrol volume 171B. In one embodiment, the processor controls thepressure in the control chamber with an on-off controller often called abang-bang controller. The on-off controller monitors the pressure in thecontrol volume 171B during a deliver stroke and open the binary valveX1B (connecting the control volume 171B to the positive reservoir 2620)when the pressure is less than a lower first limit and closes the binaryvalve X1B when the pressure is above a higher second limit. During afill stroke, the on-off controller opens the binary valve X1A(connecting the control volume 171B to the negative reservoir 2610) whenthe pressure is greater than a third limit and closes the binary valveX1A when the pressure is less than a fourth limit, where the forth limitis lower than the third limit and both the third and forth limits areless than the first limit. A plot of the pressure over time as during adeliver stroke and the subsequent FMS measurement is shown in FIG. 114.The control chamber pressure 2300 oscillates between the lower firstlimit 2312 and the higher second limit 2310 as the membrane 15 movesacross the control chamber 171B. The pressure stops oscillating betweenthe limits when the membrane 15 stops moving. The membrane 15 typicallystops moving when it contacts either the stadium steps 50 of thecassette or it contacts the control chamber surface 171B. The membrane15 may also stop moving if the outlet fluid line is occluded.

The automation computer (AC) 300 detects the end of stroke by evaluatingthe pressure signals. There are many possible algorithms to detect theend of pressure oscillation that indicate the end-of-stroke (EOS). Thealgorithms and methods to detect EOS in the section labeled “DetailedDescription of the system and Method of Measuring Change Fluid FlowRate” in U.S. Pat. No. 6,520,747 and the section describing thefiltering to detect end of stroke in U.S. Pat. No. 8,292,594 are hereinincorporated by reference.

One example of an algorithm to detect EOS, the AC 300 evaluates the timebetween the pressure crossing the first and second limits during adeliver stroke or third and fourth limits during a fill stroke. Theon-off controller opens and closes the valves X1A, X1B in response tothe pressure oscillating between the two limits as the control chambervolume changes during the fill or deliver stroke. When the membrane 15stops moving at the end-of-stroke, the pressure changes willsignificantly diminish so that the pressure no longer exceeds one orboth limits. The AC 300 may detect EOS by measuring the time between thepressure exceeding alternating limits. If the time since the pressurecrossed the last limit exceeds a predefined threshold, then the AC 300may declare an EOS. The algorithm may further include an initial periodduring which the AC 300 does not measure the time between limitcrossings.

In another example algorithm, the AC 300 evaluates the derivative of thepressure signal with respect to time. The AC 300 may declare an EOS, ifthe derivative remains below a minimum threshold for a minimum length oftime. In a further example, the minimum threshold is the average of theabsolute value of the average pressure derivative during the stroke. Thealgorithm calculates the slope (derivative with respect to time) of acurve fit to a set of data points, where the data points are taken froma moving window. The absolute value of each slope is then averaged overthe stroke to calculate the absolute value of the average pressurederivative. In another example of an EOS algorithm, the AC 300 may notinclude the pressure data until after an initial delay. The AC 300ignores the initial pressure data to avoid false EOS detections due toirregular pressure traces that occasionally occur during the early partof the stroke. In another example, the AC 300 declares an EOS only afterthe second derivative of the pressure in the later part of the strokehas remained below a threshold for a minimum time and a wait period oftime has past.

The criteria to declare an EOS may be optimized for different pumpingconditions. The optimized EOS detection conditions include the secondpressure derivative threshold, the minimum time to remain below thesecond derivative threshold, the duration of the initial delay and alength of the wait period. These EOS detection criteria may be optimizeddifferently, for example, the fill stroke from the bags 20, 22, thedeliver stroke to the patient, the fill stroke from the patient, and thedeliver stroke to the bags 20,22. Alternatively each EOS detectioncriteria may be a function of the pumping pressure in the controlchamber 171B.

Occluder

In one aspect of the disclosure, an occluder for opening/closing one ormore flexible lines may include a pair of opposed occluding members,which may be configured as resilient elements, such as flat plates madeof a spring steel (e.g., leaf springs), having a force actuatorconfigured to apply a force to one or both of the occluding members tooperate the occluder. In certain embodiments, the force actuator maycomprise an expandable or enlargable member positioned between theresilient elements. With the expandable member in a reduced sizecondition, the resilient elements may be in a flat or nearly flatcondition and urge a pinch head to engage with one or more lines so asto pinch the lines closed. However, when the expandable member urges theresilient elements apart, the resilient elements may bend and withdrawthe pinch head, releasing the lines and allowing flow through the lines.In other embodiments, the occluding members could be essentially rigidwith respect to the levels of force applied by the force actuator. Incertain embodiments, the force actuator may apply a force to one or bothopposed occluding members to increase the distance between the occludingmembers in at least a portion of the region where they are opposed toeffect opening or closing of the flexible tubing.

FIG. 99 shows an exploded view and FIG. 100 shows a partially assembledview of an illustrative embodiment of an occluder 147 that may be usedto close, or occlude, the patient and drain lines 34 and 28, and/orother lines in the cycler 14 or the set 12 (such as, for example, theheater bag line 26). The occluder 147 includes an optional pinch head161, e.g., a generally flat blade-like element that contacts the tubesto press the tubes against the door 141 and pinch the tubes closed. Inother embodiments, the function of the pinch head could be replaced byan extending edge of one or both of occluding members 165. The pinchhead 161 includes a gasket 162, such as an O-ring or other member, thatcooperates with the pinch head 161 to help resist entry of fluid (air orliquid for example) into the cycler 14 housing, e.g., in case of leakagein one of the occluded lines. The bellows gasket 162 is mounted to, andpinch head 161 passes through, a pinch head guide 163 that is mounted tothe front panel of the cycler housing, i.e., the panel exposed byopening the door 141. The pinch head guide 163 allows the pinch head 161to move in and out of the pinch head guide 163 without binding and/orsubstantial resistance to sliding motion of the pinch head 161. A pivotshaft 164 attaches a pair of opposed occluder members, comprising in theillustrated embodiment spring plates 165, that each include ahook-shaped pivot shaft bearing, e.g., like that found on standard doorhinges, to the pinch head 161. That is, the openings of shaft guides onthe pinch head 161, and the openings formed by the hook-shaped bearingson the spring plates 165 are aligned with each other and the pivot shaft164 is inserted through the openings so the pinch head 161 and thespring plates 165 are pivotally connected together. The spring plates165 may be made of any suitable material, such as steel, and may bearranged to be generally flat when unstressed. The opposite end of thespring plates 165 includes similar hook-shaped bearings, which arepivotally connected to a linear adjustor 167 by a second pivot shaft164. In this embodiment, the force actuator comprises a bladder 166 ispositioned between the spring plates 165 and arranged so that when fluid(e.g., air under pressure) is introduced into the bladder, the bladdermay expand and push the spring plates 165 away from each other in aregion between the pivot shafts 164. The bladder 166 may be attached toone or both spring plates 165 by pressure sensitive adhesive (PSA) tape.A linear adjustor 167 is fixed to the cycler housing 82 while the pinchhead 161 is allowed to float, although its movement is guided by thepinch head guide 163. The linear adjustor 167 includes slot holes at itslower end, allowing the entire assembly to be adjusted in position andthus permitting the pinch head to be appropriately positioned when theoccluder 147 is installed in the cycler 14. A turnbuckle 168 or otherarrangement may be used to help adjust the position of the linearadjustor 167 relative to the housing 82. That is, the pinch head 161generally needs to be properly positioned so that with the spring plates165 located near each other and the bladder 166 substantially emptied orat ambient pressure, the pinch head 161 suitably presses on the patientand drain lines so as to pinch the tubes closed to flow without cutting,kinking or otherwise damaging the tubes. The slot openings in the linearadjustor 167 allows for this fine positioning and fixing of the occluder147 in place. An override release device, such as provided by releaseblade 169 is optionally positioned between the spring plates 165, and asis discussed in more detail below, may be rotated so as to push thespring plates 165 apart, thereby withdrawing the pinch head 161 into thepinch head guide 163. The release blade 169 may be manually operated,e.g., to disable the occluder 147 in case of power loss, bladder 166failure or other circumstance.

Additional configurations and descriptions of certain components thatmay be instructive in constructing certain embodiments of the occluderare provided in U.S. Pat. No. 6,302,653. The spring plates 165 may beconstructed from any material that is elastically resistant to bendingforces and which has sufficient longitudinal stiffness (resistance tobending) to provide sufficient restoring force, in response to a bendingdisplacement, to occlude a desired number of collapsible tubes. In theillustrated embodiment, each spring plate is essentially flat whenunstressed and in the shape of a sheet or plate. In alternativeembodiments utilizing one or more resilient occluding members (springmembers), any occluding member(s) that is elastically resistant tobending forces and which has sufficient longitudinal stiffness(resistance to bending) to provide sufficient restoring force, inresponse to a bending displacement to occlude a desired number ofcollapsible tubes may be utilized. Potentially suitable spring memberscan have a wide variety of shapes as apparent to those of ordinary skillin the art, including, but not limited to cylindrical, prism-shaped,trapezoidal, square, or rectangular bars or beams, I-beams, ellipticalbeams, bowl-shaped surfaces, and others. Those of ordinary skill in theart can readily select proper materials and dimensions for spring plates165 based on the present teachings and the requirements of a particularapplication.

FIG. 101 shows a top view of the occluder 147 with the bladder 166deflated and the spring plates 165 located near each other and in a flator nearly flat condition. In this position, the pinch head 161 is fullyextended from the pinch head guide and the front panel of the cycler 14(i.e., the panel inside of the door 141) and enabled to occlude thepatient and drain lines. FIG. 102, on the other hand, shows the bladder166 in an inflated state in which the spring plates 165 are pushedapart, thereby retracting the pinch head 161 into the pinch head guide163. Note that the linear adjustor 167 is fixed in place relative to thecycler housing 82 and thus fixed relative to the front panel of thehousing 82. As the spring plates 165 are moved apart, the pinch head 161moves rearward relative to the front panel since the pinch head 161 isarranged to move freely in and out of the pinch head guide 163. Thiscondition prevents the pinch head 161 from occluding the patient anddrain lines and is the condition in which the occluder 147 remainsduring normal operation of the cycler 14. That is, as discussed above,various components of the cycler 14 may operate using airpressure/vacuum, e.g., the control surface 148 may operate under thedrive of suitable air pressure/vacuum to cause fluid pumping and valveoperation for the cassette 24. Thus, when the cycler 14 is operatingnormally, the cycler 14 may produce sufficient air pressure to not onlycontrol system operation, but also to inflate the bladder 166 to retractthe pinch head 161 and prevent occlusion of the patient and drain lines.However, in the case of system shut down, failure, fault or othercondition, air pressure to the bladder 166 may be terminated, causingthe bladder 166 to deflate and the spring plates 165 to straighten andextend the pinch head 161 to occlude the lines. One possible advantageof the arrangement shown is that the return force of the spring plates165 is balanced such that the pinch head 161 generally will not bind inthe pinch head guide 163 when moving relative to the pinch head guide163. In addition, the opposing forces of the spring plates 165 will tendto reduce the amount of asymmetrical frictional wear of the pivot shaftsand bushings of the assembly. Also, once the spring plates 165 are in anapproximately straight position, the spring plates 165 can exert a forcein a direction generally along the length of the pinch head 161 that isseveral times larger than the force exerted by the bladder 166 on thespring plates 165 to separate the spring plates 165 from each other andretract the pinch head 161. Further, with the spring plates 165 in aflat or nearly flat condition, the force needed to be exerted by fluidin the collapsed tubing to overcome the pinching force exerted by thepinch head 161 approaches a relatively high force required, when appliedto the spring plates at their ends and essentially parallel to the planeof the flattened spring plates, to buckle the spring plates by breakingthe column stability of the flattened spring plates. As a result, theoccluder 147 can be very effective in occluding the lines with a reducedchance of failure while also requiring a relatively small force beapplied by the bladder 166 to retract the pinch head 161. The dualspring plate arrangement of the illustrative embodiment may have theadditional advantage of significantly increasing the pinching forceprovided by the pinch head, for any given force needed to bend thespring plate, and/or for any given size and thickness of spring plate.

In some circumstances, the force of the occluder 147 on the lines may berelatively large and may cause the door 141 to be difficult to open.That is, the door 141 must oppose the force of the occluder 147 when thepinch head 161 is in contact with and occluding lines, and in some casesthis may cause the latch that maintains the door 141 in a closed stateto be difficult or impossible to operate by hand. Of course, if thecycler 14 is started and produces air pressure to operate, the occluderbladder 166 can be inflated and the occluder pinch head 161 retracted.However, in some cases, such as with a pump failure in the cycler 14,inflation of the bladder 166 may be impossible or difficult. To allowopening of the door, the occluder 147 may include a manual release. Inthis illustrative embodiment, the occluder 147 may include a releaseblade 169 as shown in FIGS. 99 and 100 which includes a pair of wingspivotally mounted for rotary movement between the spring plates 165.When at rest, the release blade wings may be aligned with the springs asshown in FIG. 100, allowing the occluder to operate normally. However,if the spring plates 165 are in a flat condition and the pinch head 161needs to be retracted manually, the release blade 169 may be rotated,e.g., by engaging a hex key or other tool with the release blade 169 andturning the release blade 169, so that the wings push the spring plates165 apart. The hex key or other tool may be inserted through an openingin the housing 82 of the cycler 14, e.g., an opening near the left sidehandle depression in the cycler housing 82, and operated to disengagethe occluder 147 and allow the door 141 to be opened.

Pump Volume Delivery Measurement

In another aspect of the invention, the cycler 14 may determine a volumeof fluid delivered in various lines of the system 10 without the use ofa flowmeter, weight scale or other direct measurement of fluid volume orweight. For example, in one embodiment, a volume of fluid moved by apump, such as a pump in the cassette 24, may be determined based onpressure measurements of a gas used to drive the pump. In oneembodiment, a volume determination can be made by isolating two chambersfrom each other, measuring the respective pressures in the isolatedchambers, allowing the pressures in the chambers to partially orsubstantially equalize (by fluidly connecting the two chambers) andmeasuring the pressures. Using the measured pressures, the known volumeof one of the chambers, and an assumption that the equalization occursin an adiabatic way, the volume of the other chamber (e.g., a pumpchamber) can be calculated. In one embodiment, the pressures measuredafter the chambers are fluidly connected may be substantially unequal toeach other, i.e., the pressures in the chambers may not have yetcompletely equalized. However, these substantially unequal pressures maybe used to determine a volume of the pump control chamber, as explainedbelow.

For example, FIG. 103 shows a schematic view of a pump chamber 181 ofthe cassette 24 and associated control components and inflow/outflowpaths. In this illustrative example, a liquid supply, which may includethe heater bag 22, heater bag line 26 and a flow path through thecassette 24, is shown providing a liquid input at the upper opening 191of the pump chamber. The liquid outlet is shown in this example asreceiving liquid from the lower opening 187 of the pump chamber 181, andmay include a flow path of the cassette 24 and the patient line 34, forexample. The liquid supply may include a valve, e.g., including thevalve port 192, that can be opened and closed to permit/impede flow toor from the pump chamber 181. Similarly, the liquid outlet may include avalve, e.g., including the valve port 190, that can be opened and closedto permit/impede flow to or from the pump chamber 181. Of course, theliquid supply could include any suitable arrangement, such as one ormore solution containers, the patient line, one or more flow paths inthe cassette 24 or other liquid source, and the liquid outlet couldlikewise include any suitable arrangement, such as the drain line, theheater bag and heater bag line, one or more flow paths in the cassette24 or other liquid outlet. Generally speaking, the pump chamber 181(i.e., on the left side of the membrane 14 in FIG. 103) will be filledwith an incompressible liquid, such as water or dialysate, duringoperation. However, air or other gas may be present in the pump chamber181 in some circumstances, such as during initial operation, priming, orother situations as discussed below. Also, it should be understood thatalthough aspects of the invention relating to volume and/or pressuredetection for a pump are described with reference to the pumparrangement of the cassette 24, aspects of the invention may be usedwith any suitable pump or fluid movement system.

FIG. 103 also shows schematically to the right of the membrane 15 andthe control surface 1482 (which are adjacent each other) a controlchamber 171B, which may be formed as a void or other space in the matingblock 170A associated with the pump control region 1482 of the controlsurface 1482 for the pump chamber 181, as discussed above. It is in thecontrol chamber 171B that suitable air pressure is introduced to causethe membrane 15/control region 1482 to move and effect pumping of liquidin the pump chamber 181. The control chamber 171B may communicate with aline L0 that branches to another line L1 and a first valve X1 thatcommunicates with a pressure source 84 (e.g., a source of air pressureor vacuum). The pressure source 84 may include a piston pump in whichthe piston is moved in a chamber to control a pressure delivered to thecontrol chamber 171B, or may include a different type of pressure pumpand/or tank(s) to deliver suitable gas pressure to move the membrane15/control region 1482 and perform pumping action. The line L0 alsoleads to a second valve X2 that communicates with another line L2 and areference chamber 174 (e.g., a space suitably configured for performingthe measurements described below). The reference chamber 174 alsocommunicates with a line L3 having a valve X3 that leads to a vent orother reference pressure (e.g., a source of atmospheric pressure orother reference pressure). Each of the valves X1, X2 and X3 may beindependently controlled. Pressure sensors may be arranged, e.g., onesensor at the control chamber 171B and another sensor at the referencechamber 174, to measure pressure associated with the control chamber andthe reference chamber. These pressure sensors may be positioned and mayoperate to detect pressure in any suitable way. The pressure sensors maycommunicate with the control system 16 for the cycler 14 or othersuitable processor for determining a volume delivered by the pump orother features.

As mentioned above, the valves and other components of the pump systemshown in FIG. 103 can be controlled so as to measure pressures in thepump chamber 181, the liquid supply and/or liquid outlet, and/or tomeasure a volume of fluid delivered from the pump chamber 181 to theliquid supply or liquid outlet. Regarding volume measurement, onetechnique used to determine a volume of fluid delivered from the pumpchamber 181 is to compare the relative pressures at the control chamber171B to that of the reference chamber 174 in two different pump states.By comparing the relative pressures, a change in volume at the controlchamber 171B can be determined, which corresponds to a change in volumein the pump chamber 181 and reflects a volume delivered from/receivedinto the pump chamber 181. For example, after the pressure is reduced inthe control chamber 171B during a pump chamber fill cycle (e.g., byapplying negative pressure from the pressure source through open valveX1) so as to draw the membrane 15 and pump control region 1482 intocontact with at least a portion of the control chamber wall (or toanother suitable position for the membrane 15/region 1482), valve X1 maybe closed to isolate the control chamber from the pressure source, andvalve X2 may be closed, thereby isolating the reference chamber 174 fromthe control chamber 171B. Valve X3 may be opened to vent the referencechamber to ambient pressure, then closed to isolate the referencechamber. With valve X1 closed and the pressures in the control chamberand reference chamber measured, valve X2 is then opened to allow thepressure in the control chamber and the reference chamber to start toequalize. The initial pressures of the reference chamber and the controlchamber, together with the known volume of the reference chamber andpressures measured after equalization has been initiated (but not yetnecessarily completed) can be used to determine a volume for the controlchamber. This process may be repeated at the end of the pump deliverycycle when the sheet 15/control region 1482 are pushed into contact withthe spacer elements 50 of the pump chamber 181. By comparing the controlchamber volume at the end of the fill cycle to the volume at the end ofthe delivery cycle, a volume of liquid delivered from the pump can bedetermined.

Conceptually, the pressure equalization process (e.g., at opening of thevalve X2) is viewed as happening in an adiabatic way, i.e., without heattransfer occurring between air in the control and reference chambers andits environment. The conceptual notion is that there is an imaginarypiston located initially at the valve X2 when the valve X2 is closed,and that the imaginary piston moves in the line L0 or L2 when the valveX2 is opened to equalize the pressure in the control and referencechambers. Since (a) the pressure equalization process happens relativelyquickly, (b) the air in the control chamber and the reference chamberhas approximately the same concentrations of elements, and (c) thetemperatures are similar, the assumption that the pressure equalizationhappens in an adiabatic way may introduce only small error into thevolume measurements. Also, in one embodiment, the pressures taken afterequalization has been initiated may be measured before substantialequalization has occurred—further reducing the time between measuringthe initial pressures and the final pressures used to determine the pumpchamber volume. Error can be further reduced, for example, by using lowthermal conductivity materials for the membrane 15/control surface 1482,the cassette 24, the control chamber 171B, the lines, the referencechamber 174, etc., so as to reduce heat transfer.

Given the assumption that an adiabatic system exists between the statewhen the valve X2 is closed until after the valve X2 is opened and thepressures equalize, the following applies:PV ^(γ)=Constant  (1)

where P is pressure, V is volume and γ is equal to a constant (e.g.,about 1.4 where the gas is diatomic, such as air). Thus, the followingequation can be written to relate the pressures and volumes in thecontrol chamber and the reference chamber before and after the openingof valve X2 and pressure equalization occurs:PrVr ^(γ) +PdVd ^(γ)=Constant=PfVf ^(γ)  (2)

where Pr is the pressure in the reference chamber and lines L2 and L3prior to the valve X2 opening, Vr is the volume of the reference chamberand lines L2 and L3 prior to the valve X2 opening, Pd is the pressure inthe control chamber and the lines L0 and L1 prior to the valve X2opening, Vd is the volume of the control chamber and the lines L0 and L1prior to the valve X2 opening, Pf is the equalized pressure in thereference chamber and the control chamber after opening of the valve X2,and Vf is the volume of the entire system including the control chamber,the reference chamber and the lines L0, L1, L2, and L3, i.e., Vf=Vd+Vr.Since Pr, Vr, Pd, Pf and γ are known, and Vf=Vr+Vd, this equation can beused to solve for Vd. (Although reference is made herein to use of a“measured pressure” in determining volume values, etc., it should beunderstood that such a measured pressure value need not necessarily beany particular form, such as in psi units. Instead, a “measuredpressure” or “determined pressure” may include any value that isrepresentative of a pressure, such as a voltage level, a resistancevalue, a multibit digital number, etc. For example, a pressuretransducer used to measure pressure in the pump control chamber mayoutput an analog voltage level, resistance or other indication that isrepresentative of the pressure in the pump control chamber. The rawoutput from the transducer may be used as a measured pressure, and/orsome modified form of the output, such as a digital number generatedusing an analog output from the transducer, a psi or other value that isgenerated based on the transducer output, and so on. The same is true ofother values, such as a determined volume, which need not necessarily bein a particular form such as cubic centimeters. Instead, a determinedvolume may include any value that is representative of the volume, e.g.,could be used to generate an actual volume in, say, cubic centimeters.

In an embodiment of a fluid management system (“FMS”) technique todetermine a volume delivered by the pump, it is assumed that pressureequalization upon opening of the valve X2 occurs in an adiabatic system.Thus, Equation 3 below gives the relationship of the volume of thereference chamber system before and after pressure equalization:Vrf=Vri(Pf/Patm)^(−(1/γ))  (3)

where Vrf is the final (post-equalization) volume of the referencechamber system including the volume of the reference chamber, the volumeof the lines L2 and L3 and the volume adjustment resulting from movementof the “piston”, which may move to the left or right of the valve X2after opening, Vri is the initial (pre-equalization) volume of thereference chamber and the lines L2 and L3 with the “piston” located atthe valve X2, Pf is the final equalized pressure after the valve X2 isopened, and Patm is the initial pressure of the reference chamber beforevalve X2 opening (in this example, atmospheric pressure). Similarly,Equation 4 gives the relationship of the volume of the control chambersystem before and after pressure equalization:Vdf=Vdi(Pf/Pdi)^(−(1/γ))  (4)

where Vdf is the final volume of the control chamber system includingthe volume of the control chamber, the volume of the lines L0 and L1,and the volume adjustment resulting from movement of the “piston”, whichmay move to the left or right of the valve X2 after opening, Vdi is theinitial volume of the control chamber and the lines L0 and L1 with the“piston” located at the valve X2, Pf is the final pressure after thevalve X2 is opened, and Pdi is the initial pressure of the controlchamber before valve X2 opening.

The volumes of the reference chamber system and the control chambersystem will change by the same absolute amount after the valve X2 isopened and the pressure equalizes, but will differ in sign (e.g.,because the change in volume is caused by movement of the “piston” leftor right when the valve X2 opens), as shown in Equation 5:ΔVr=(−1)ΔVd  (5)

(Note that this change in volume for the reference chamber and thecontrol chamber is due only to movement of the imaginary piston. Thereference chamber and control chamber will not actually change in volumeduring the equalization process under normal conditions.) Also, usingthe relationship from Equation 3, the change in volume of the referencechamber system is given by:ΔVr=Vrf−Vri=Vri(−1+(Pf/Patm)^(−(1/γ)))  (6)

Similarly, using Equation 4, the change in volume of the control chambersystem is given by:ΔVd=Vdf−Vdi=Vdi(−1+(Pf/Pdi)^(−(1/γ)))  (7)

Because Vri is known, and Pf and Patm are measured or known, ΔVr can becalculated, which according to Equation 5 is assumed to be equal to(−)ΔVd. Therefore, Vdi (the volume of the control chamber system beforepressure equalization with the reference chamber) can be calculatedusing Equation 7. In this embodiment, Vdi represents the volume of thecontrol chamber plus lines L0 and L1, of which L0 and L1 are fixed andknown quantities. Subtracting L0 and L1 from Vdi yields the volume ofthe control chamber alone. By using Equation 7 above, for example, bothbefore (Vdi1) and after (Vdi2) a pump operation (e.g., at the end of afill cycle and at the end of a discharge cycle), the change in volume ofthe control chamber can be determined, thus providing a measurement ofthe volume of fluid delivered by (or taken in by) the pump. For example,if Vdi1 is the volume of the control chamber at the end of a fillstroke, and Vdi2 is the volume of the control chamber at the end of thesubsequent delivery stroke, the volume of fluid delivered by the pumpmay be estimated by subtracting Vdi1 from Vdi2. Since this measurementis made based on pressure, the volume determination can be made fornearly any position of the membrane 15/pump control region 1482 in thepump chamber 181, whether for a full or partial pump stroke. However,measurement made at the ends of fill and delivery strokes can beaccomplished with little or no impact on pump operation and/or flowrate.

One aspect of the invention involves a technique for identifyingpressure measurement values that are to be used in determining a volumefor the control chamber and/or other purposes. For example, althoughpressure sensors may be used to detect a pressure in the control chamberand a pressure in the reference chamber, the sensed pressure values mayvary with opening/closing of valves, introduction of pressure to thecontrol chamber, venting of the reference chamber to atmosphericpressure or other reference pressure, etc. Also, since in oneembodiment, an adiabatic system is assumed to exist from a time beforepressure equalization between the control chamber and the referencechamber until after equalization, identifying appropriate pressurevalues that were measured as close together in time may help to reduceerror (e.g., because a shorter time elapsed between pressuremeasurements may reduce the amount of heat that is exchanged in thesystem). Thus, the measured pressure values may need to be chosencarefully to help ensure appropriate pressures are used for determininga volume delivered by the pump, etc.

As mentioned, L3 of FIG. 103 may have a valve X3 which leads to a vent.In some embodiments, this vent may communicate with the atmosphere or,in other embodiments, another reference pressure. In some embodiments,this vent may be connected via a valve to the control chamber 171B suchthat the control chamber may be vented (see, e.g., FIG. 95). In priordevices the vent has been used to bring a control chamber 171B from anegative pressure after a fill stroke to ambient pressure beforepositive pressurization of the control chamber 171B. This brings thecontrol chamber 171B to a higher starting pressure before connection tothe pressure source 84 and consequently minimizes the depletion ofpressure in a positive pressure source or reservoir 84. As a result apump supplying a positive pressure reservoir 84 would be required to runless frequently.

On the other hand, it has since been determined that venting a controlchamber 171B which is already at a positive pressure to a lower pressurebefore subsequently positively repressurizing the chamber for an FMSmeasurement may be advantageous in some scenarios. Though this new steprequires additional work (e.g. pump runtime) to keep the pressure source84 at its pressure set point, it may be done to help mitigate anypossible undesirable effects from back pressure (e.g. due to an occludedline leading to or from the associated pumping chamber, or due to apartial occlusion). Additionally, this may help to increase the overallaccuracy of volume measurement and fluid accounting. One possible reasonfor this is that a pump chamber outlet valve 190—in this case apneumatically operated membrane valve—may not close as efficiently whenthe control chamber 171B remains positively pressurized.

In some embodiments, a control system 16 of a cycler 14 may vent thecontrol chamber 171B before taking a measurement to determine fluidvolume delivered or filled. Additionally, in some embodiments, thecontrol system 16 of a cycler 14 may vent a first control chamber 171Bbefore performing a pumping operation with a second control chamberincluded in the installed cassette 24.

In the example embodiment shown in FIG. 103, this venting or backpressure relief may be accomplished by opening valves X2 and X3 andclosing valve X1. Thus, the control chamber 171B may be placed intocommunication with the vent via the reference chamber 174. In otherembodiments, of course, a control chamber 171B may be placed into moredirect communication with a vent. For example, an additional valveassociated with a fluid path in direct communication with the vent maybe included. Any other suitable configuration may also be used.

In some embodiments, the control chamber 171B may be vented by placingthe control chamber 171B into fluid communication with the vent for asuitable or predetermined period of time. In other embodiments, tocontrol venting of a control chamber 171B, the control system 16 of thecycler 14 may use data from a pressure sensor associated with one orboth of the control chambers 171B or reference chamber 174 (or in alocation fluidly connectable to the control chamber, such as, forexample, a pressure distribution module). In such embodiments, data fromthe pressure sensor(s) may be used to determine whether or not thecontrol chamber 171B has been sufficiently vented. Once a determinationis made that the control chamber 171B has been sufficiently vented, thecontrol system 16 of the cycler 14 may close the appropriate valve toisolate the control chamber 171B from the vent. In order for the controlsystem 16 to determine that the control chamber 171B has beensufficiently vented, the control chamber 171B pressure need notnecessarily fully equalize with that of the vent.

In some embodiments, in order to relieve back pressure in a controlchamber 171B, it may instead be subjected to a negative pressure sourcefor an appropriate or predetermined period of time. In such embodiments,the control chamber 171B may be placed into communication with apressure source 84. In the example embodiment shown in FIG. 103, thismay be accomplished by opening valve X1 and closing at least valve X3.In the case of a positively pressurized control chamber 171B, thepressure source to which the control chamber 171B is connected may be anegative pressure source. In some embodiments, the control system 16 ofthe cycler 14 may only open a valve to the negative pressure source fora brief period of time. The brief period of time may be of a durationsufficient to bring the pressure in the control chamber 171B to within apre-determined range of a predetermined value (in an example, this maybe approximately atmospheric pressure), before it is allowed to equalizewith the pressure source. In other embodiments, the valve X1 may bemodulated to produce the same effect. If it is a vari-valve, its orificeopening may be modulated by the controller; whereas if it is a binaryvalve, the controller may modulate the rate and magnitude of pressuredelivery across the valve using, for example, pulse-width-modulation.

For purposes of explanation, FIG. 104 shows a plot of illustrativepressure values for the control chamber and the reference chamber from apoint in time before opening of the valve X2 until some time after thevalve X2 is opened to allow the pressure in the chambers to equalize. Inthis illustrative embodiment, the pressure in the control chamber ishigher than the pressure in the reference chamber before equalization,but it should be understood that the control chamber pressure may belower than the reference chamber pressure before equalization in somearrangements, such as during and/or at the end of a fill stroke. Also,the plot in FIG. 104 shows a horizontal line marking the equalizationpressure, but it should be understood that this line is shown forclarity only. The equalization pressure in general will not be knownprior to opening of the valve X2. In this embodiment, the pressuresensors sense pressure at a rate of about 2000 Hz for both the controlchamber and the reference chamber, although other suitable samplingrates could be used. Before opening of the valve X2, the pressures inthe control chamber and the reference chamber are approximatelyconstant, there being no air or other fluid being introduced into thechambers. Thus, the valves X1 and X3 will generally be closed at a timebefore opening of the valve X2. Also, valves leading into the pumpchamber, such as the valve ports 190 and 192, may be closed to preventinfluence of pressure variations in the pump chamber, the liquid supplyor liquid outlet.

At first, the measured pressure data is processed to identify theinitial pressures for the control chamber and reference chambers, i.e.,Pd and Pr. In one illustrative embodiment, the initial pressures areidentified based on analysis of a 10-point sliding window used on themeasured pressure data. This analysis involves generating a best fitline for the data in each window (or set), e.g., using a least squarestechnique, and determining a slope for the best fit line. For example,each time a new pressure is measured for the control chamber or thereference chamber, a least squares fit line may be determined for a dataset including the latest measurement and the 9 prior pressuremeasurements. This process may be repeated for several sets of pressuredata, and a determination may be made as to when the slope of the leastsquares fit lines first becomes negative (or otherwise non-zero) andcontinues to grow more negative for subsequent data sets (or otherwisedeviates from a zero slope). The point at which the least squares fitlines begin to have a suitable, and increasing, non-zero slope may beused to identify the initial pressure of the chambers, i.e., at a timebefore the valve X2 is opened.

In one embodiment, the initial pressure value for the reference chamberand the control chamber may be determined to be in the last of 5consecutive data sets, where the slope of the best fit line for the datasets increases from the first data set to the fifth data set, and theslope of the best fit line for the first data set first becomes non-zero(i.e., the slope of best fit lines for data sets preceding the firstdata set is zero or otherwise not sufficiently non-zero). For example,the pressure sensor may take samples every ½ millisecond (or othersampling rate) starting at a time before the valve X2 opens. Every timea pressure measurement is made, the cycler 14 may take the most recentmeasurement together with the prior 9 measurements, and generate a bestfit line to the 10 data points in the set. Upon taking the next pressuremeasurement (e.g., ½ millisecond later), the cycler 14 may take themeasurement together with the 9 prior measurements, and again generate abest fit line to the 10 points in the set. This process may be repeated,and the cycler 14 may determine when the slope of the best fit line fora set of 10 data points first turns non-zero (or otherwise suitablysloped) and, for example, that the slope of the best fit line for κsubsequent sets of 10 data points increases with each later data set. Toidentify the specific pressure measurement to use, one technique is toselect the third measurement in the 5^(th) data set (i.e., the 5^(th)data set with which it was found that the best fit line has beenconsistently increasing in slope and the 1^(st) measurement is thepressure measurement that was taken earliest in time) as the measurementto be used as the initial pressure for the control chamber or thereference chamber, i.e., Pd or Pr. This selection was chosen usingempirical methods, e.g., plotting the pressure measurement values andthen selecting which point best represents the time when the pressurebegan the equalization process. Of course, other techniques could beused to select the appropriate initial pressure.

In one illustrative embodiment, a check may be made that the times atwhich the selected Pd and Pr measurements occurred were within a desiredtime threshold, e.g., within 1-2 milliseconds of each other. Forexample, if the technique described above is used to analyze the controlchamber pressure and the reference chamber pressure and identify apressure measurement (and thus a point in time) just before pressureequalization began, the times at which the pressures were measuredshould be relatively close to each other. Otherwise, there may have beenan error or other fault condition that invalidates one or both of thepressure measurements. By confirming that the time at which Pd and Proccurred are suitably close together, the cycler 14 may confirm that theinitial pressures were properly identified.

To identify when the pressures in the control chamber and the referencechamber have equalized such that measured pressures for the chamber canbe used to reliably determine pump chamber volume, the cycler 14 mayanalyze data sets including a series of data points from pressuremeasurements for both the control chamber and the reference chamber,determine a best fit line for each of the data sets (e.g., using a leastsquares method), and identify when the slopes of the best fit lines fora data set for the control chamber and a data set for the referencechamber are first suitably similar to each other, e.g., the slopes areboth close to zero or have values that are within a threshold of eachother. When the slopes of the best fit lines are similar or close tozero, the pressure may be determined to be equalized. The first pressuremeasurement value for either data set may be used as the final equalizedpressure, i.e., Pf. In one illustrative embodiment, it was found thatpressure equalization occurred generally within about 200-400milliseconds after valve X2 is opened, with the bulk of equalizationoccurring within about 50 milliseconds. Accordingly, the pressure in thecontrol and reference chambers may be sampled approximately 400-800times or more during the entire equalization process from a time beforethe valve X2 is opened until a time when equalization has been achieved.

In some cases, it may be desirable to increase the accuracy of thecontrol chamber volume measurement using an alternate FMS technique.Substantial differences in temperature between the liquid being pumped,the control chamber gas, and the reference chamber gas may introducesignificant errors in calculations based on the assumption that pressureequalization occurs adiabatically. Waiting to make pressure measurementsuntil full equalization of pressure between the control chamber and thereference chamber may allow an excessive amount of heat transfer tooccur. In one aspect of the invention, pressure values for the pumpchamber and reference chamber that are substantially unequal to eachother, i.e., that are measured before complete equalization hasoccurred, may be used to determine pump chamber volume.

In one embodiment, heat transfer may be minimized, and adiabaticcalculation error reduced, by measuring the chamber pressures throughoutthe equalization period from the opening of valve X2 through fullpressure equalization, and selecting a sampling point during theequalization period for the adiabatic calculations. In one embodiment ofan APD system, measured chamber pressures that are taken prior tocomplete pressure equalization between the control chamber and thereference chamber can be used to determine pump chamber volume. In oneembodiment, these pressure values may be measured about 50 ms after thechambers are first fluidly connected and equalization is initiated. Asmentioned above, in one embodiment, complete equalization may occurabout 200-400 ms after the valve X2 is opened. Thus, the measuredpressures may be taken at a point in time after the valve X2 is opened(or equalization is initiated) that is about 10% to 50% or less of thetotal equalization time period. Said another way, the measured pressuresmay be taken at a point in time at which 50-70% of pressure equalizationhas occurred (i.e., the reference and pump chamber pressures havechanged by about 50-70% of the difference between the initial chamberpressure and the final equalized pressure. Using a computer-enabledcontroller, a substantial number of pressure measurements in the controland reference chambers can be made, stored and analyzed during theequalization period (for example, 40-100 individual pressuremeasurements). Among the time points sampled during the first 50 ms ofthe equalization period, there is a theoretically optimized samplingpoint for conducting the adiabatic calculations (e.g., see FIG. 104 inwhich the optimized sampling point occurs at about 50 ms after openingof the valve X2). The optimized sampling point may occur at a time earlyenough after valve X2 opening to minimize thermal transfer between thegas volumes of the two chambers, but not so early as to introducesignificant errors in pressure measurements due to the properties of thepressure sensors and delays in valve actuation. However, as can be seenin FIG. 104, the pressures for the pump chamber and reference chambersmay be substantially unequal to each other at this point, and thusequalization may not be complete. (Note that in some cases, it may betechnically difficult to take reliable pressure measurements immediatelyafter the opening of valve X2, for example, because of the inherentinaccuracies of the pressure sensors, the time required for valve X2 tofully open, and the rapid initial change in the pressure of either thecontrol chamber or the reference chamber immediately after the openingof valve X2.)

During pressure equalization, when the final pressure for the controlchamber and reference chambers are not the same, Equation 2 becomes:_PriVri ^(γ) +PdiVdi ^(γ)=Constant=PrfVrf ^(γ) +PdfVdf ^(γ)  (8)

where: Pri=pressure in the reference chamber prior to opening valve X2,Pdi=pressure in the control chamber prior to opening valve X2, Prf=finalreference chamber pressure, Pdf=final control chamber pressure.

An optimization algorithm can be used to select a point in time duringthe pressure equalization period at which the difference between theabsolute values of ΔVd and ΔVr is minimized (or below a desiredthreshold) over the equalization period. (In an adiabatic process, thisdifference should ideally be zero, as indicated by Equation 5. In FIG.104 the point in time at which the difference between the absolutevalues of ΔVd and ΔVr is minimized occurs at the 50 ms line, marked“time at which final pressures identified.”) First, pressure data can becollected from the control and reference chambers at multiple points j=1through n between the opening of valve X2 and final pressureequalization. Since Vri, the fixed volume of the reference chambersystem before pressure equalization, is known, a subsequent value forVrj (reference chamber system volume at sampling point j after valve X2has opened) can be calculated using Equation 3 at each sampling pointPrj along the equalization curve. For each such value of Vrj, a valuefor ΔVd can be calculated using Equations 5 and 7, each value of Vrjthus yielding Vdij, a putative value for Vdi, the volume of the controlchamber system prior to pressure equalization. Using each value of Vrjand its corresponding value of Vdij, and using Equations 3 and 4, thedifference in the absolute values of ΔVd and ΔVr can be calculated ateach pressure measurement point along the equalization curve. The sum ofthese differences squared provides a measure of the error in thecalculated value of Vdi during pressure equalization for each value ofVrj and its corresponding Vdij. Denoting the reference chamber pressurethat yields the least sum of the squared differences of |ΔVd| and |ΔVr|as Prf, and its associated reference chamber volume as Vrf, the datapoints Prf and Pdf corresponding to Vrf can then be used to calculate anoptimized estimate of Vdi, the initial volume of the control chambersystem.

One method for determining where on the equalization curve to capture anoptimized value for Pdf and Prf is as follows:

-   -   1) Acquire a series of pressure data sets from the control and        reference chambers starting just before the opening of valve X2        and ending with Pr and Pd becoming close to equal. If Pri is the        first reference chamber pressure captured, then the subsequent        sampling points in FIG. 104 will be referred to as Prj=Pr1, Pr2,        . . . Prn.    -   2) Using Equation 6, for each Prj after Pri, calculate the        corresponding ΔVrj where j represents the jth pressure data        point after Pri.        ΔVrj=Vrj−Vri=Vri(−1+(Prj/Pri)^((1/γ))    -   3) For each such ΔVrj calculate the corresponding Vdij using        Equation 7. For example:        ΔVr1=Vri*(−1+(Pr1/Pri)^(−(1/γ)))        ΔVd1=−ΔVr1        -   Therefore,            Vdi1=ΔVd1/(−1+(Pd1/Pdi)^(−(1/γ)))            Vdin=ΔVdn/(−1+(Pdn/Pdi)^(−(1/γ)))            Having calculated a set of n control chamber system initial            volumes (Vdi1 to Vdin) based on the set of reference chamber            pressure data points Pr1 to Prn during pressure            equalization, it is now possible to select the point in            time (f) that yields an optimized measure of the control            chamber system initial volume (Vdi) over the entire pressure            equalization period.    -   4) Using Equation 7, for each Vdi1 through Vdin, calculate all        ΔVdj,k using control chamber pressure measurements Pd for time        points k=1 to n.        -   For the Vdi corresponding to Pr1:            ΔVd1,1=Vdi1*(−1+(Pd1/Pdi)^(−(1/γ)))            ΔVd1,2=Vdi1*(−1+(Pd2/Pdi)^(−(1/γ)))            ΔVd1,n=Vdi1*(−1+(Pdn/Pdi)^(−(1/γ)))        -   For the Vdi corresponding to Prn:            ΔVdn,1=Vdin*(−1+(Pd1/Pdi)^(−(1/γ)))            ΔVdn,2=Vdin*(−1+(Pd2/Pdi)^(−(1/γ)))            ΔVdn,n=Vdin*(−1+(Pdn/Pdi)^(−(1/γ)))    -   5) Take the sum-square error between the absolute values of the        ΔVr's and ΔVdj,k's

$S_{1} = {\sum\limits_{k = 1}^{n}\left( \left| {\Delta\; V_{{d\; 1},k}} \middle| {- \left| {\Delta\; V_{rk}} \right|} \right. \right)^{2}}$

-   -   -   [S1 represents the sum-square error of |ΔVd| minus |ΔVr|            over all data points during the equalization period when            using the first data point Pr1 to determine Vdi, the control            chamber system initial volume, from Vr1 and ΔVr.]

$S_{2} = {\sum\limits_{k = 1}^{n}\left( \left| {\Delta\; V_{{d\; 2},k}} \middle| {- \left| {\Delta\; V_{rk}} \right|} \right. \right)^{2}}$

-   -   -   [S2 represents the sum-square error of |ΔVr| minus |ΔVd|            over all data points during the equalization period when            using the second data point Pr2 to determine Vdi, the            control chamber system initial volume, from Vr2 and ΔVr.]

$S_{n} = {\sum\limits_{k = 1}^{n}\;\left( {{{\Delta\; V_{{d\; n},k}}} - {{\Delta\; V_{rk}}}} \right)^{2}}$

-   -   6) The Pr data point between Pr1 and Prn that generates the        minimum sum-square error S from step 5 (or a value that is below        a desired threshold) then becomes the chosen Prf, from which Pdf        and an optimized estimate of Vdi, the control chamber initial        volume, can then be determined. In this example, Pdf occurs at,        or about, the same time as Prf.    -   7) The above procedure can be applied any time that an estimate        of the control chamber volume is desired, but can preferably be        applied at the end of each fill stroke and each delivery stroke.        The difference between the optimized Vdi at the end of a fill        stroke and the optimized Vdi at the end of a corresponding        delivery stroke can be used to estimate the volume of liquid        delivered by the pump.

Air Detection

Another aspect of the invention involves the determination of a presenceof air in the pump chamber 181, and if present, a volume of air present.Such a determination can be important, e.g., to help ensure that apriming sequence is adequately performed to remove air from the cassette24 and/or to help ensure that air is not delivered to the patient. Incertain embodiments, for example, when delivering fluid to the patientthrough the lower opening 187 at the bottom of the pump chamber 181, airor other gas that is trapped in the pump chamber may tend to remain inthe pump chamber 181 and will be inhibited from being pumped to thepatient unless the volume of the gas is larger than the volume of theeffective dead space of pump chamber 181. As discussed below, the volumeof the air or other gas contained in pump chambers 181 can be determinedin accordance with aspects of the present invention and the gas can bepurged from pump chamber 181 before the volume of the gas is larger thanthe volume of the effective dead space of pump chamber 181.

A determination of an amount of air in the pump chamber 181 may be madeat the end of a fill stroke, and thus, may be performed withoutinterrupting a pumping process. For example, at the end of a fill strokeduring which the membrane 15 and the pump control region 1482 are drawnaway from the cassette 24 such that the membrane 15/region 1482 arebrought into contact with the wall of the control chamber 171, the valveX2 may be closed, and the reference chamber vented to atmosphericpressure, e.g., by opening the valve X3. Thereafter, the valves X1 andX3 may be closed, fixing the imaginary “piston” at the valve X2. Thevalve X2 may then be opened, allowing the pressure in the controlchamber and the reference chamber to equalize, as was described abovewhen performing pressure measurements to determine a volume for thecontrol chamber.

If there is no air bubble in the pump chamber 181, the change in volumeof the reference chamber, i.e., due to the movement of the imaginary“piston,” determined using the known initial volume of the referencechamber system and the initial pressure in the reference chamber, willbe equal to the change in volume of the control chamber determined usingthe known initial volume of the control chamber system and the initialpressure in the control chamber. (The initial volume of the controlchamber may be known in conditions where the membrane 15/control region1482 are in contact with the wall of the control chamber or in contactwith the spacer elements 50 of the pump chamber 181.) However, if air ispresent in the pump chamber 181, the change in volume of the controlchamber will actually be distributed between the control chamber volumeand the air bubble(s) in the pump chamber 181. As a result, thecalculated change in volume for the control chamber using the knowninitial volume of the control chamber system will not be equal to thecalculated change in volume for the reference chamber, thus signalingthe presence of air in the pump chamber.

If there is air in the pump chamber 181, the initial volume of thecontrol chamber system Vdi is actually equal to the sum of the volume ofthe control chamber and lines L0 and L1 (referred to as Vdfix) plus theinitial volume of the air bubble in the pump chamber 181, (referred toas Vbi), as shown in Equation 9:Vdi=Vbi+Vdfix  (9)

With the membrane 15/control region 1482 pressed against the wall of thecontrol chamber at the end of a fill stroke, the volume of any air spacein the control chamber, e.g., due to the presence of grooves or otherfeatures in the control chamber wall, and the volume of the lines L0 andL1—together Vdfix—can be known quite accurately. (Similarly, with themembrane 15/control region 1482 pressed against the spacer elements 50of the pump chamber 181, the volume of the control chamber and the linesL0 and L1 can be known accurately.) After a fill stroke, the volume ofthe control chamber system is tested using a positive control chamberpre-charge. Any discrepancy between this tested volume and the testedvolume at the end of the fill stroke may indicate a volume of airpresent in the pump chamber. Substituting from Equation 9 into Equation7, the change in volume of the control chamber ΔVd is given by:ΔVd=(Vbi+Vdfix)(−1+(Pdf/Pdi)^(−(1/γ)))  (10)

Since ΔVr can be calculated from Equation 6, and we know from Equation 5that ΔVr=(−1) ΔVd, Equation 10 can be re-written as:(−1)ΔVr=(Vbi+Vdfix)(−1+(Pdf/Pdi)^(−(1/γ)))  (11)

and again as:Vbi=(−1)ΔVr/(−1+(Pdf/Pdi)^(−(1/γ)) −Vdfix  (12)

Accordingly, the cycler 14 can determine whether there is air in thepump chamber 181, and the approximate volume of the bubble usingEquation 12. This calculation of the air bubble volume may be performedif it is found, for example, that the absolute values of ΔVr (asdetermined from Equation 6) and ΔVd (as determined from Equation 7 usingVdi=Vdfix) are not equal to each other. That is, Vdi should be equal toVdfix if there is no air present in the pump chamber 181, and thus theabsolute value for ΔVd given by Equation 7 using Vdfix in place of Vdiwill be equal to ΔVr.

After a fill stroke has been completed, and if air is detected accordingto the methods described above, it may be difficult to determine whetherthe air is located on the pump chamber side or the control side of themembrane 15. Air bubbles could be present in the liquid being pumped, orthere could be residual air on the control (pneumatic) side of the pumpmembrane 15 because of a condition (such as, for example, an occlusion)during pumping that caused an incomplete pump stroke, and incompletefilling of the pump chamber. At this point, an adiabatic FMS measurementusing a negative pump chamber pre-charge can be done. If this FMS volumematches the FMS volume with the positive precharge, then the membrane isfree to move in both directions, which implies that the pump chamber isonly partially filled (possibly, for example, due to an occlusion). Ifthe value of the negative pump chamber pre-charge FMS volume equals thenominal control chamber air volume when the membrane 15/region 1482 isin contact with the inner wall of the control chamber, then it ispossible to conclude that there is an air bubble in the liquid on thepump chamber side of the flexible membrane.

Polytropic FMS for Pump Volume Delivery Measurement

Introduction to FMS

In another aspect of the disclosure, the cycler 14 in FIG. 1 maydetermine a volume of fluid delivered in various lines of the system 10without the use of a flowmeter, weight scale or other direct measurementof fluid volume or weight. For example, in one embodiment, a volume offluid moved by a diaphragm pump, such as a pneumatically drivendiaphragm pump including a cassette 24, may be determined based onpressure measurements of a gas used to drive the pump.

In one embodiment, the volume determination is accomplished with aprocess herein referred to as the two-chamber Fluid Measurement System(2-chamber FMS) process. The volume of fluid pumped by the diaphragmpump may be calculated from the change in the volume of the pneumaticchamber on one side of the diaphragm. The volume of the pneumaticchamber may be measured at the end of each fill and deliver stroke, sothat the difference in volume between sequential measurements is thevolume of fluid moved by the pump.

The volume of the pneumatic chamber or first chamber is measured withthe 2-chamber FMS process that comprises closing the liquid valves intoand out of the diaphragm pump, isolating the first chamber from a secondchamber of a known volume (reference chamber), pre-charging the firstchamber to a first pressure, while pre-charging the second chamber to asecond pressure, then fluidically connecting the two chambers, andrecording at least the initial and final pressures in each chamber asthe pressures equalize. The volume of first chamber may be calculatedfrom at least the initial and final pressures and the known volume ofthe second chamber.

If the first chamber is precharged to a pressure above the pressure inthe second chamber then the 2-chamber FMS process is referred to aspositive FMS or +FMS. If the first chamber is precharged to a pressureless than the pressure in the second chamber, then the 2-chamber FMSprocess is referred to as negative or −FMS. Referring now to FIG. 105,the first chamber is the control chamber 6171 and the second chamber isthe reference chamber 6212.

The form of the algorithm to calculate the first chamber volume maydepend on the heat transfer characteristics of the first and secondchamber and the fluid lines that connect the two chambers. The amount ofheat transfer between the structure and the gases during equalizationaffects the pressures in both the first and second chamber during andafter equalization. During equalization, the gas in the chamber with thehigher pressure expands toward the other chamber. This expanding gaswill cool to a lower temperature and consequently a lower pressure. Thecooling of the expanding gas and the loss in pressure may be moderatedor reduced by heat transfer from the warmer structure. At the same time,the gas in the chamber initially at a lower pressure is compressedduring equalization. The temperature of this compressing gas will risealong with the pressure. The heating of the compressing gas and the risein pressure may be moderated or reduced by heat transfer from the coolerstructure.

The relative importance of heat transfer between the structure (chamberwalls, solid material within the chambers) and the gas is a function ofthe average hydraulic diameter of the chamber, the thermal diffusivityof the gas and the duration of the equalization process. In one example,the two volumes are filled with heat absorbing material such as foam orother matrix that provide enough surface area and thermal mass that thegas temperatures are constant in each chamber during pressureequalization, so that the expansion and compression processes can bemodeled as isothermal. In another example, the two chambers are sizedand shaped to provide negligible heat transfer, so the expansion andcompression processes can be modeled as adiabatic. In another example,the shape and size of the control chamber 6171 changes from measurementto measurement. In measurements after a fill stroke when the controlchamber 6171 is small and all the gas is relatively near the chamberwall 6170 or the diaphragm 6148, the heat transfer between the gas andthe structure is significant. In measurements after a deliver stroke,the control chamber 6171 is large and open, so that much of the gas isrelatively isolated from the chamber walls 6170 or diagphragm 6148 andheat transfer to the gas is neglible. In measurements after a partialstroke the heat transfer between the structure and the gas issignificant, but not sufficient to assure constant temperature. In allthese measurements, the expansion and compression processes can bemodeled as polytropic and the relative importance of heat transfer canbe varied from one measurement to the next. A polytropic model canaccurately model the equalization process for all geometries and capturethe effects of different levels of heat transfer in the first and thesecond chambers. A more detailed model of the equalization process willmore accurately determine the volume of the first chamber from theknowledge of the pressures and the volume of the second chamber.

This section describes an algorithm to calculate the volume of the firstchamber 6171 for a polytropic 2-chamber FMS process. The firstsub-section describes the two volume FMS or 2-chamber FMS process for anexemplary arrangement of volumes, pressure sources, valves and pressuresensors. The next sub-section conceptually describes the polytropic FMSalgorithm for data from a +FMS process and then presents the exactequations to calculate the first volume from the pressure data. The nextsub-section presents the concept and equations of the polytropic FMSalgorithm for data from a −FMS process. The last sub-section presentsthe process to calculate the volume of the first chamber 6171 usingeither set of equations.

The model being described can be applied to any system or apparatus thatuses a pneumatically actuated diaphragm pump. The components of thesystem include a diaphragm pump having at least one pump chamber inletor outlet with a valved connection to either a fluid source or fluiddestination; a pneumatic control chamber separated from the pump chamberby a diaphragm that provides positive or negative pressure to the pumpchamber for fluid delivery or filling; the pneumatic control chamber hasa valved connection to a reference chamber of known volume and to apositive or negative pressure source; a controller controls the valvesof the system and monitors pneumatic pressure in the control chamber andreference chamber. An example of the system is illustrated schematicallyin FIG. 105, although the specific arrangement of inlets, outlets andfluid and pneumatic conduits and valves can vary to some degree fromthis illustration. The following description will use a peritonealdialysis cycler and pump cassette as an example, but the invention is byno means limited to this particular application.

Hardware for 2-Chamber FMS Process

Referring now to FIG. 105, which schematically presents elements of thecycler and the cassette 624 that are involved in the 2-chamber FMSprocess. The cassette 624 includes two liquid valves 6190, 6192 that arefluidically connected to a liquid supply 6193 and liquid outlet 6191.The cassette 624 includes a diaphragm pump with a variable liquid volumepump chamber 6181 separated by a flexible membrane 6148 from the controlchamber 6171. The control chamber 6171 volume is defined by the membrane6148 and the chamber wall 6170. The control chamber 6171 is the firstchamber of unknown volume described above.

A control line 6205 also leads to a connection valve 6214 thatcommunicates with a reference line 6207 and a reference chamber 6212(e.g., a space suitably configured for performing the measurementsdescribed below). The reference chamber 6212 is the second chamber witha known volume described above. The reference chamber 6212 alsocommunicates with an exit line 6208 having a second valve 6216 thatleads to a vent 6226 to atmospheric pressure. In another example thevent 6226 may be a reservoir controlled to a desired pressure by one ormore pneumatic pumps, a pressure sensor and controller. Each of thevalves 6220, 6214 and 6216 may be independently controlled by thecontroller 61100.

The pressure source 6210 is selectively connected to the control chamber6171 via lines 6209 and 6205. The pressure source 6210 may include oneor more separate reservoirs which are held at specified and differentpressures by one or more pneumatic pumps. Each pneumatic pump may becontrolled by the controller 61100 to maintain the specified pressure ineach reservoir as measured by pressure sensors. A first valve 6220 maycontrol the fluid connection between the pressure source 6210 and thecontrol chamber 6171. The controller 61100 may selectively connect oneof the reservoirs in the pressure source 6210 to line 6209 to controlthe pressure in the control chamber as measured by pressure sensor 6222.In some examples, the controller 1100 may be part of a larger controlsystem in the APD cycler.

The control chamber 6171 is connected to the control pressure sensor6222 via line 6204. A reference pressure sensor 6224 may be connected tothe reference chamber 6212 via line 6203. The pressure sensors 6222,6224 may be an electromechanical pressure sensor that measures theabsolute pressure such as the MPXH6250A by Freescale Semiconductors ofJapan. The control pressure sensor 6222 and the reference pressuresensor 6224 are connected to the controller 61100, which records thecontrol and reference pressures for subsequent volume calculations.Alternatively, the pressure sensors 6222, 6224 may be relative pressuresensors that measure the pressure in the control and reference chambersrelative to the ambient pressure and the controller 61100 may include anabsolute pressure sensor to measure the ambient pressure. The controller61100 may combine the relative pressure signals from sensors 6222, 6224and the absolute ambient pressure sensor to calculate the absolutepressures in the control chamber 6171 and reference chamber 6212respectively.

The valves and other components of the FMS hardware shown in FIG. 105can be controlled by the controller 61100 to execute the 2-chamber FMSprocess and measure the resulting pressures in control chamber 6171 andin the reference chamber 6212, then calculate the volume of the controlchamber 6171. The controller 61100 may be a single micro-processor ormultiple processors. In one example, the pressure signals are receivedby an A-D board and buffered before being passed to the 61100controller. In another example, a field-programmable-gate-array (FPGA)may handle all the I/O between the controller 61100 and the valves andsensors. In another example, the FPGA may filter, store and/or processthe pressure data to calculate volume of the control chamber.

2-Chamber FMS Process in APD Cycler

Referring now to pressure vs time plot of FIG. 106 and the elements inFIG. 105. An exemplary pumping and measurement process is described inthe plot of the control chamber pressure 6300 and the reference chamberpressure 6302 verses time. As described above, after closing the inletvalve 6192 and opening the outlet valve 6190, the chamber pressure iscontrolled to a positive value 6305 that pushed fluid out of the pumpchamber 6181 during the deliver stroke 6330. At the end of the deliverstroke 6330, the outlet fluid valve is closed and a +FMS process mayoccur to measure the volume of the control chamber 6171. The FMS processas described elsewhere may consist of bringing the control chamberpressure 6330 to a precharging pressure 6307 and allowing a period ofpressure stabilization 6338, followed by a equalization process 6340. Inother examples, the control chamber pressure 6330 may be returned tonear atmospheric pressure before being increased to the prechargepressure 6307. At the end of equalization process 6340, the referencechamber pressure 6302 and possibly the control chamber pressure 6300 canbe returned to near atmospheric values.

The fill stroke 6320 occurs after opening the inlet valve 6192 andbrings the control chamber pressure 6300 to a negative pressure 6310,while the reference chamber remains near atmospheric, or at a measuredand constant pressure. The negative pressure pulls fluid into the pumpchamber 6181. At the end of the fill stroke 6320, the inlet valve 6192is closed and a +FMS process may occur to determine the volume of thecontrol chamber 6171. In some embodiments, a −FMS process may occurafter the +FMS process. The −FMS process may comprise precharging thecontrol chamber to negative pressure 6317, allowing pressurestabilization 6342 and finally an equalization process 6345. The controlchamber volume determined from −FMS process may be compared to thecontrol chamber volume determined from the +FMS process to determinewhether there is a volume of air or gas in the pump chamber 6181. (Forexample, if the pump chamber includes an air trap comprising ribs orstandoffs on the pump chamber rigid wall, air can accumulate among thestandoffs, the diaphragm at its full excursion can be prevented fromcompressing it by the standoffs, and the air may not be detected by a+FMS process alone). In one example, a −FMS process occurs after thedeliver stroke 6330.

The +FMS and −FMS processes are described in more detail by referring tothe flow chart in FIG. 107, elements in FIG. 105, and the pressure vs.time plots of FIGS. 108A, 108B. The 2-chamber FMS process begins withstep 6410 where the position of the membrane 6148 is fixed. The positionof the membrane 6148 may be fixed by closing both hydraulic valves 6190,6192. In some examples, the position of membrane 6148 will vary as thecontrol chamber pressure changes, if gas bubbles are present in theliquid. However the volume of incompressible liquid between thehydraulic valves 6190, 6192 is fixed. The 2-chamber FMS process willgenerally measure the volume of air or gas on both sides of the membrane6148, so any bubbles in the pump chamber 6181 on the liquid side of themembrane 6148 are included in the measured volume of the control chamber6171.

In step 6412, the control chamber 6171 is fluidically isolated from thereference chamber 6212 by closing connection valve 6214. Then thereference chamber 6212 and control chamber 6171 are fluidically isolatedfrom each other in step 6412. In an embodiment, the reference chamber6212 is connected to the vent 6226 in step 6424 by opening the secondvalve 6216. The controller 61100 holds the second valve 6216 open, untilreference pressure sensor 6224 indicates that the reference pressure hasreached ambient pressure. Alternatively, the controller 61100 maycontrol the second valve 6216 to achieve a desired initial referencepressure in the reference chamber 6212 as measured by the referencepressure sensor 6224. Alternatively, the connection valve 6214 may beclosed and the second valve 6216 is open before the FMS process begins.In step 6428, once the desired pressure in the reference chamber 6212 isachieved, the second valve 6216 is closed, which fluidically isolatesthe reference chamber 6212. The reference chamber steps 6424 and 6428may be programmed to occur concurrently with the control chamber steps6414 and 6418.

In step 6414, the control chamber 6171 is pressurized to a desiredpressure by connecting the control chamber 6171 to the pressure source6210 by opening the first valve 6220. The controller 61100 monitors thepressure in the control chamber 6171 with pressure sensor 6222 andcontrols the first valve 6220 to achieve a desired precharge pressure.The desired precharge pressure may be significantly above the initialreference pressure of the reference chamber 6212 or significantly belowthe initial reference pressure. In one example, the control chamber 6171is precharged to approximately 40 kPa above the reference pressure for a+FMS process. In another example, the control chamber 6171 is prechargedto approximately 40 kPa below the reference pressure for a −FMS process.In other embodiments, the precharge pressures may be any pressure withinthe range of 10% to 180% of the initial reference pressure.

The controller 61100 closes the first valve 6220 in step 6418 andmonitors the pressure in the control chamber 6171 with pressure sensor6222. The pressure in the control chamber 6171 may move toward ambientpressure during step 6418 due to gas thermally equalizing with thecontrol chamber wall 6170 and membrane 6148. A large change in pressureduring step 6418 may indicate a pneumatic or liquid leak that wouldinvalidate a measurement. The 2-chamber FMS process may be aborted orthe calculated volume of the control chamber 6171 may be discarded ifthe rate of pressure change exceeds a pre-determined allowable rate. Therate of pressure change may be examined after a delay from thepressurization step 6414 to allow the gas in the control chamber 6171 toapproach thermal equilibrium with the boundaries 6172, 6148 of thecontrol chamber 6171. In one example, the maximum allowed rate ofpressure change during step 6418 is 12 kPA/sec. The 2-chamber FMSprocess may be aborted and restarted if the rate of pressure changeexceeds this predetermined value. In another embodiment, the maximumallowable rate of pressure change is a function of—and will vary basedon—the calculated control chamber volume. In one example, the maximumallowed pressure change is 3 kPA/sec for a 25 ml volume and 25 kPA/secfor 2 ml volume. In one example, the FMS process may be carried tocompletion regardless of the leak rate resulting in a calculated volumeof the control chamber 6171. The calculated volume may be discarded andthe FMS process restarted if the measured rate of pressure changeexceeds the allowable limit for the calculated control chamber volume.

The control chamber 6171 and the reference chamber 6212 are fluidicallyconnected in step 6432, when the controller 61100 opens the connectionvalve 6214 between the two chambers. The controller 61100 monitors thepressures in each chamber with the pressure sensors 6222, 6224 as thepressure in the control chamber 6171 and reference chamber 6212equalize. The controller 61100 may record the initial pressure pair andat least one pressure pair at the end of equalization in step 6432. Apressure pair refers to a signal from the control pressure sensor 6222and a signal from the reference pressure sensor 6224 recorded atapproximately the same time. Step 6432 extends from a period of timejust before the connection valve 6214 is open to a point in time, whenthe pressure in the control chamber 6171 and reference chamber 6212 arenearly equal.

The 2-chamber FMS process is completed in step 6436, where the recordedpairs of pressures are used to calculate the volume of the controlchamber 6171. The calculation of the control chamber 6171 volume isdescribed in detail below.

The +FMS process is sketched as pressure vs. time plot in FIG. 108A.Reference numbers corresponding to those of the steps in FIG. 107 areincluded to indicate where those steps are depicted in FIG. 108A. Thepressure of the control chamber 6171 is plotted as line 6302. Thepressure of the reference chamber is plotted as line 6304. The pressurevs. time plot begins after steps 6410, 6412, 6424, 6428 of FIG. 107 havebeen completed. At this point the pressure in the reference chamber 6212is at the desired reference pressure 6312. The pressure in the controlchamber 6171 begins at an arbitrary pressure 6306 and during step 6414increases to the precharge pressure 6316. The arbitrary pressure 6306may be the pressure of the control chamber 6171 at the conclusion of aprevious pumping operation. In another embodiment, the arbitrarypressure 6306 may atmospheric pressure. The control chamber pressure6302 may drop during step 6418. In step 6432, the control chamberpressure 6302 and reference chamber pressure 6304 equalize toward anequilibrium pressure 6324.

The −FMS process is sketched as pressure vs. time plot in FIG. 108B. Thepressure of the control chamber 6171 (FIG. 105) is plotted as line 6302.The pressure of the reference chamber 6312 (FIG. 105) is plotted as line6304. The horizontal time axis is divided in periods that correspond tothe process steps identified with the same reference numbers in FIG.107. The pressure vs. time plot begins when the pressure in thereference chamber 6212 (line 6302) is at the desired reference pressure6312 and the pressure in the control chamber 6171 (line 6304) is at anarbitrary pressure. During step 6414, the control chamber pressure 6302decreases to the negative precharge pressure 6317. The control chamberpressure 6302 may rise during step 6418 as the gas cooled by the suddenexpansion of step 6414 is heated by the control chamber walls 6172,6148. In step 6432, the control chamber pressure 6302 and referencechamber pressure 6304 equalize toward an equilibrium pressure 6324.

Polytropic +FMS Algorithm

Referring now to FIG. 105, for illustrative purposes, the equalizationprocess involves the fluid volumes of three distinct structures: controlchamber 6171, reference chamber 6212 and the manifold passages 6204,6205, 6207, 6209 connecting the two chambers 6171, 6212. In one example,each structure has significantly different hydraulic diameters and thusdifferent levels of heat transfer between the structure and the gas. Inthis example, the reference chamber 6212 has an approximately cubicshape with a hydraulic diameter of approximately 3.3 cm. Heat transferduring the approximately 30 microsecond equalization process isnegligibly small and the gas in the reference chamber 6212 volume islikely to be compressed adiabatically, and can be modeled as such. Incontrast, in an exemplary construction, the manifold passages 6204,6205, 6207, 6209, have an approximately 0.2 cm hydraulic diameter, whichis about 15 times smaller than the hydraulic diameter of the referencechamber 6212 volume. Heat transfer in the manifold passages 6204, 6205,6207, 6209 is high and the gas passing through these passages 6204,6205, 6207, 6209 is more likely to compress or expand isothermally atapproximately the temperature of the manifold walls. The hydraulicdiameter of the control chamber 6171 in this example has a minimum ofvalue of approximately 0.1 cm when the pumping chamber 6181 is full ofliquid at the end of a fill stroke and the control chamber 6171 is at aminimum volume. The hydraulic diameter of the control chamber 6171 inthis example has a maximum value of approximately 2.8 cm when thepumping chamber 6181 has delivered the liquid and the control chamber6171 is at a maximum volume. The expansion of gas in the control chamber6171 can be more appropriately modeled with a polytropic coefficientthat varies with the size of the control chamber 6171. When the controlchamber 6171 volume is at a minimum and the expansion process will benearly isothermal, the polytropic coefficient can be set toapproximately 1. When the control chamber 6171 is at a maximum and theexpansion process is near adiabatic, the polytropic coefficient may beset to approximately the ratio of specific heats (cp/cv), which equals1.4 for air. For 2-chamber FMS measurements at partial strokes, theexpansion process will occur with significant heat transfer, but notenough to be isothermal. The polytropic coefficient may be set to avalue between 1 and 1.4 for measurements at partial strokes. Since thevolume of the control chamber 6171 is the unknown quantity of thisanalysis, the polytropic coefficient for the control chamber 6171 may bebased on an estimate of control chamber 6171 volume.

Referring now to FIG. 109A, the gas in the structures of the controlchamber 6510, the reference chamber 6520 and the manifold lines 6530,6531 can be modeled as three gas masses, 6512, 6532, 6522 that do notmix, but expand, contract, and move through the structures 6510, 6520,6530, 6531. Conceptually, for modeling purposes, these masses 6512,6532, 6522 are each a closed-system that may move, change size andexchange energy with the structures, but mass may not enter nor exit theclosed-system. The closed-system model is a well understood concept inthermodynamics and fluid dynamics. These masses may also be referred toas a control chamber system 6512, reference chamber system 6522 and amanifold or interconnecting line system 6532.

The volume of the control chamber 6510 can be calculated from themeasured control chamber 6510 and reference chamber 6520 pressures basedon thermodynamic models of the three masses 6512, 6532, 6522. Thecontrol chamber mass or gas 6512 is the gas that occupies the controlchamber 6510 at the end of the equalization process. The referencechamber gas 6522 is the gas that occupies the reference chamber 6520 atthe beginning of the equalization process. The manifold gas 6532 fillsthe balance of the structure between the control chamber gas 6512 andthe reference chamber gas 6522, including a connecting conduit betweenthe control and reference chambers.

The volume and temperature of the three closed-systems, 6512, 6532, 6522may then calculated from initial conditions, pressure pairs, heattransfer assumptions and the constraint of a fixed total volume for thethree closed-systems. The pressure equalization can be modeled with adifferent polytropic coefficient for each volume 6510, 6520, 6530, 6531to capture the relative importance of heat transfer in each. Theconstant mass, ideal gas and polytropic process equations for the threesystems, 6512, 6532, 6522 can be combined and arranged to calculate thevolume of the control chamber 6510. The following paragraphs describethe derivation of one or more sets of equations that allow calculationof the control chamber 6510 volume based on pressures measured duringthe pressure equalization step of the FMS process (see, 6432 of FIGS.107 and 108A).

Description of Closed Systems for +FMS

The upper image in FIG. 109A presents the position of the threeclosed-systems 6512, 6532, 6522 at the start of pressure equalization inthe +FMS process. The lower image presents the positions of the threeclosed systems 6512, 6532, 6522 at the end of the pressure equalization.During the equalization process, the locations of the closed systems6512, 6532, 6522 are between the two extremes presented in FIG. 109A. Byway of an example, neither the control chamber system 6512 nor thereference chamber system 6522 fill their respective structures. Thefollowing paragraphs present the closed systems 6512, 6532, 6522 in moredetail.

The control chamber gas system 6512 is the gas that fills the controlchamber 6510 after pressure equalization. Before pressure equalization,the control chamber gas system 6512 is compressed to the prechargepressure that is higher than the final equalization pressure andtherefore does not occupy the entire control chamber 6510. The controlchamber gas system 6512 may be modeled as expanding in a polytropicprocess during pressure equalization of the +FMS process, where thepressure and the volume are related by:p _(f) V _(CC) ^(nCC)=constant

where p_(f) is the equalized pressure, V_(CC) is the volume of thecontrol chamber 6510, and nCC is the polytropic coefficient for thecontrol chamber 6510.

The reference gas system 6522 is the gas that occupies the entirereference volume 6520 before equalization. The reference gas system 6522is compressed during equalization as the higher pressure gas in thecontrol chamber 6510 expands and pushed the manifold gas system 6532into the reference chamber 6520 In one example shown in FIG. 93, thereference chambers (depicted as 174 in FIG. 93) are sufficiently open ordevoid of interior features/elements that compression or expansionprocesses during pressure equalization may be modeled as adiabatic. Inthis case, the polytropic coefficient (n) may be set equal toapproximately the specific heat ratio of the gas present in the chamber.The pressure and the volume of the reference chamber gas 6522 arerelated by:p _(R0) V _(Ref) ^(nR)=constant

where p_(R0) is the initial reference pressure, V_(Ref) is the volume ofthe reference chamber, and nR is the specific heat ratio for the gas inthe reference chamber (nR=1.4 air). In another example, where thechamber 6520 is at least partially filled with a heat absorbing materialsuch as open cell foam, wire mesh, particles, etc. that provides for anear-isothermal expansion, the polytropic coefficient for the referencechamber (nR) may have a value of approximately 1.0.

In the +FMS process, the conduit or manifold gas system 6532 occupiesall of the volume of the interconnecting volume 6530, 6531 and afraction 6534 of the control chamber 6510 before equalization. Afterequalization, the conduit gas system 6532 occupies the interconnectingvolume 6530, 6531 and part of the reference volume 6520. The portion ofthe conduit gas system 6532 that exists in interconnecting volume 6530on the control chamber side of the valve 6540 is herein labeled as 6533.The portion of the conduit gas system 6532 that exits in theinterconnecting volume 6531 on the reference chamber side of the valve6540 is referred to as 6535. The portion of the conduit gas system 6532that exist in the control chamber 6510 pre-equalization is hereinlabeled as 6534. The portion of the conduit gas system 6532 that existsin the reference chamber 6520 after equalization is referred to as 6536.

In one example the interconnecting volumes 6530 and 6531 may be narrowpassages that provide high heat transfer and assure the conduit gassystem 6532 in volumes 6530 and 6531 is near the temperature of thesolid boundaries or walls of the passages. The temperature of thestructure surrounding the interconnecting volumes 6530, 6531 or manifoldpassages is herein referred to as the wall temperature (T_(w)). Inanother example, the temperature of the conduit gas system 6532 involumes 6530, 6531 is in part a function of the wall temperature. Theportion of the conduit or manifold gas system in the control chamber6534 may be modeled with the same temperature as control chamber gassystem 6512. The control chamber portion of the conduit gas system 6534experiences the same expansion as the control chamber gas system 6512and may be conceived of as having the same temperature as the controlchamber gas system 6512. The portion of the lines or manifold gas systemin the reference chamber 6536 may be modeled with a temperature that isin part a function of the wall temperature. In another example, thereference chamber portion of the conduit gas system 6536 may be modeledas not interacting thermally with the boundaries of the referencechamber 6520, so that the temperature of the conduit gas system portion6536 is a function of the wall temperature and the reference chamber6520 pressures.

The equations in this section use the following nomenclature:

-   -   variables    -   γ: specific heat ratio    -   n: polytropic coefficient    -   p: pressure    -   V: volume    -   T: temperature

superscripts:

-   -   n: polytropic coefficient    -   nCC: polytropic coefficient for the control chamber    -   nR: polytropic coefficient for the reference chamber subscripts:    -   c: control chamber system    -   CC: physical control chamber    -   f: value at end of equalization    -   i: i^(th) value    -   IC: physical interconnecting volume or manifold passages    -   IC_R: physical interconnecting volume on the reference chamber        side of valve    -   IC_CC: physical interconnecting volume on the control chamber        side of valve    -   l: lines or interconnecting/manifold system    -   0: value at start of equalization    -   pmp: pump    -   r: reference system    -   Ref: physical reference chamber    -   w: wall of interconnecting volume

The equations for the control chamber 6510 may derived from theconceptual model of the three separate mass systems in FIG. 109A and theunderstanding that the total volume of the control chamber mass 6510,reference chamber mass 6520 and interconnecting volumes mass 6530, 6531is fixed. This relationship can be expressed as the sum of the volumechanges of each closed system 6512, 6522, 6532 being zero for eachi^(th) set of values from the start to the end of pressure equalization:

$\begin{matrix}{{0 = {\begin{matrix}{{change}\mspace{14mu}{in}\mspace{14mu}{volume}\mspace{14mu}{of}} \\{{control}\mspace{14mu}{chamber}\mspace{14mu}{mass}}\end{matrix} + \begin{matrix}{{change}\mspace{14mu}{in}\mspace{14mu}{volume}\mspace{14mu}{of}} \\{{interconnecting}\mspace{14mu}{mass}}\end{matrix} + \begin{matrix}{{change}\mspace{14mu}{in}\mspace{14mu}{volume}\mspace{14mu}{of}} \\{{reference}\mspace{14mu}{chamber}\mspace{14mu}{mass}}\end{matrix}}}\mspace{79mu}{0 = {{\Delta\; V_{ci}} + {\Delta\; V_{ri}} + {\Delta\; V_{li}}}}} & (13)\end{matrix}$where the i^(th) value of ΔΔV_(ci), ΔV_(ri), ΔV_(li) represents thesevalues at the same point in time. Equations can be developed for thevolume change of the control chamber gas system (ΔV_(ci)), the referencegas system (ΔV_(ri)), and the conduit gas system (ΔV_(li)) based on thepressure/volume relationship of a polytropic process and the ideal gaslaw. The equation for the i^(th) volume change of the control chambergas system 6512 is equal to the i^(th) volume of the control chambermass 6512 less the volume of the control chamber mass 6512 at the startof equalization. The volume of the control chamber mass 6512 at time iis calculated from the volume of the control chamber 6510 times theratio of the final control chamber 6510 pressure over the controlchamber 6510 pressure at time i, raised to one over the polytropiccoefficient for the control chamber 6510:

$\begin{matrix}{{\begin{matrix}{{current}\mspace{14mu}{change}\mspace{14mu}{in}\mspace{14mu}{volume}} \\{{of}\mspace{14mu}{control}\mspace{14mu}{chamber}\mspace{14mu}{mass}}\end{matrix} = {\begin{matrix}{{current}\mspace{14mu}{volume}\mspace{14mu}{of}} \\{{control}\mspace{14mu}{chamber}\mspace{14mu}{mass}}\end{matrix} - \begin{matrix}{{initial}\mspace{14mu}{volume}\mspace{14mu}{of}} \\{{control}\mspace{14mu}{chamber}\mspace{14mu}{mass}}\end{matrix}}}{{\Delta\; V_{ci}} = {{V_{CC}\left( \frac{P_{{CC}\mspace{11mu} f}}{P_{{CC}\mspace{11mu} i}} \right)}^{1/{nCC}} - {V_{CC}\left( \frac{P_{{CC}\mspace{11mu} f}}{P_{{CC}\mspace{11mu} 0}} \right)}^{1/{nCC}}}}} & (14)\end{matrix}$

The equation for the reference gas system volume change (ΔV_(r)) isderived from the pressure/volume relationship for a polytropic process.The equation for the i^(th) volume change of the reference chamber gassystem 6522 is equal to the i^(th) volume of the reference chamber mass6522 less the volume of the reference chamber mass 6522 at the start ofequalization. The volume of the reference chamber mass 6522 at time i iscalculated from the structural volume of the reference chamber 6520times the ratio of the initial reference chamber 6520 pressure over thereference chamber 6520 pressure at time i, raised to one over thepolytropic coefficient for the reference chamber 6520:

$\begin{matrix}{{\begin{matrix}{{current}\mspace{14mu}{change}\mspace{14mu}{in}\mspace{14mu}{volume}} \\{{of}\mspace{14mu}{reference}\mspace{14mu}{chamber}\mspace{14mu}{mass}}\end{matrix} = {\begin{matrix}{{current}\mspace{14mu}{volume}\mspace{14mu}{of}} \\{{reference}\mspace{14mu}{chamber}\mspace{14mu}{mass}}\end{matrix} - \begin{matrix}{{initial}\mspace{14mu}{volume}\mspace{14mu}{of}} \\{{reference}\mspace{14mu}{chamber}\mspace{14mu}{mass}}\end{matrix}}}{{\Delta\; V_{ri}} = {{V_{ref}\left( \frac{P_{{Ref}\mspace{11mu} 0}}{P_{{Ref}\mspace{11mu} i}} \right)}^{1/{nR}} - V_{REF}}}} & (15)\end{matrix}$

The equation for the volume change of the interconnecting gas system6532 (ΔV_(l)) is derived from the constant mass gas of the system(V*ρ=constant). The equation for the i^(th) volume change of the conduitgas system 6532 is equal the current volume of the system less theoriginal volume of the interconnecting gas system 6532. The currentvolume of the interconnecting or line gas system 6532 is the initialvolume times the ratio of initial over current density of the system.The initial volume of the interconnecting gas system 6532 is the sum ofthe volumes 6534, 6533 and 6535 pictured in the upper image FIG. 109A:

$\begin{matrix}{{\begin{matrix}{{current}\mspace{14mu}{change}\mspace{14mu}{in}\mspace{14mu}{volume}} \\{{of}\mspace{14mu}{interconnecting}\mspace{14mu}{mass}}\end{matrix} + \begin{matrix}{{current}\mspace{14mu}{volume}\mspace{14mu}{of}} \\{{interconnecting}\mspace{14mu}{mass}}\end{matrix} + \begin{matrix}{{intial}\mspace{14mu}{volume}\mspace{14mu}{of}} \\{{interconnecting}\mspace{14mu}{mass}}\end{matrix}}{{\Delta\; V_{li}} = {{\left( {{\Delta\; V_{cf}} + V_{IC}} \right)\frac{\rho_{lo}}{\rho_{li}}} - {\left( {{\Delta\; V_{cf}} + V_{IC}} \right).}}}} & (16)\end{matrix}$

The density terms ρ_(l0), ρ_(li) are the average density of the gases inthe conduit gas system at the start of equalization and at some point,i, during equalization. The conduit gas system 6532 includes gases asdifferent temperatures and pressures. The conduit gas system 6532includes gas in the volume in the control chamber 6510 in a volumelabeled 6534, gas in manifold passages on the control chamber side ofthe valve 6540 labeled 6533, gas in manifold passages on the referencechamber side of the valve 6540 labeled 6535, and gas in the referencechamber labeled 6536.

These four equations may be combined develop an expression for thevolume (V_(CC)) of the control chamber 6510 as a function of themeasured pressure pairs at the start of pressure equalization (P_(CC 0),P_(Ref 0)), at any point during the equalization (P_(CC i), P_(Ref i)),the control chamber 6510 pressure at approximately the end ofequalization (P_(CC f)) and the fixed volumes of the reference chamber(V_(Ref)) and interconnecting volume (V_(IC)):

$\begin{matrix}{V_{CC} = \frac{{V_{ref}\left\lbrack {\left( \frac{P_{{Ref}\mspace{11mu} 0}}{P_{{Ref}\mspace{11mu} i}} \right)^{1/{nR}} - 1} \right\rbrack} + {V_{IC}\left( {\frac{\rho_{lo}}{\rho_{li}} - 1} \right)}}{\left\lbrack {1 - \left( \frac{P_{{CC}\mspace{11mu} f}}{P_{{CC}\mspace{11mu} i}} \right)^{1/{nCC}}} \right\rbrack + {\left\lbrack {\left( \frac{P_{{CC}\mspace{11mu} f}}{P_{{CC}\mspace{11mu} o}} \right)^{1/{nCC}} - 1} \right\rbrack\left( \frac{\rho_{lo}}{\rho_{li}} \right)}}} & (17)\end{matrix}$

where the densities of the manifold or line system 6532 (ρ_(l 0),ρ_(1 i)) are evaluated with the initial pressure pairs (P_(CC 0),P_(Ref 0)) and any pressure pair (P_(CC i), P_(Ref i)) duringequalization along with the associated temperatures as described below.

The densities of the conduit gas system (ρ_(l 0), ρ_(l i)) in equations(16) may be calculated from the volume-weighted average density for eachphysical volume (i.e. control chamber 6510, reference chamber 6520, andinterconnecting volumes 6530, 6531):

$\begin{matrix}{{\rho_{li} = \frac{{\rho_{CCi}\left( {{\Delta\; V_{cf}} - {\Delta\; V_{ci}}} \right)} + {\rho_{{IC}\;\_\;{CC}}V_{{IC}\;\_\;{CC}}} + {\rho_{{IC}\;\_\; R}V_{{IC}\;\_\; R}} - {\rho_{ri}\Delta\; V_{ri}}}{\left( {{\Delta\; V_{cf}} - {\Delta\; V_{ci}} + V_{{IC}\;\_\;{CC}} + V_{{IC}\;\_\; R} + {\Delta\; V_{ri}}} \right)}}{\rho_{CCi} = {\frac{P_{CCi}}{R\mspace{11mu} T_{CCi}} = {{density}\mspace{14mu}{of}\mspace{14mu}{gas}\mspace{14mu}{in}\mspace{14mu}{control}\mspace{14mu}{chamber}}}}{\rho_{{IC}\;\_\;{CCi}} = {\frac{P_{CCi}}{R\mspace{11mu} T_{{IC}\;\_\;{CC}}} = \begin{matrix}{{density}\mspace{14mu}{of}\mspace{14mu}{gas}\mspace{14mu}{in}\mspace{14mu}{manifold}\mspace{14mu}{line}} \\{{on}\mspace{14mu}{control}\mspace{14mu}{chamber}\mspace{14mu}{side}\mspace{14mu}{of}\mspace{14mu}{value}}\end{matrix}}}{\rho_{{IC}\;\_\;{Ri}} = {\frac{P_{Refi}}{R\mspace{11mu} T_{{IC}\;\_\;{CC}}} = \begin{matrix}{{density}\mspace{14mu}{of}\mspace{14mu}{gas}\mspace{14mu}{in}\mspace{14mu}{manifold}\mspace{14mu}{line}} \\{{on}\mspace{14mu}{reference}\mspace{14mu}{chamber}\mspace{14mu}{side}\mspace{14mu}{of}\mspace{14mu}{value}}\end{matrix}}}{\rho_{ri} = {\frac{P_{Refi}}{R\mspace{11mu} T_{lr}} = \begin{matrix}{{density}\mspace{14mu}{of}\mspace{14mu}{gas}\mspace{14mu}{in}} \\{{reference}\mspace{14mu}{chamber}}\end{matrix}}}} & (18)\end{matrix}$

where R is the universal gas constant for air, the temperatures,T_(IC_CC), T_(IC_R), T_(lr), may be functions in part of the temperatureof the interconnecting volume walls. In another example, thetemperatures, T_(IC_CC), T_(IC_R), T_(lr), may be functions in part ofthe temperature of the interconnecting volume walls and the gastemperature of the control chamber (T_(CCi)). In another example, thetemperatures, T_(IC_CC), T_(IC_R), T_(lr), may be the interconnectingwall temperature (T_(w)). In another example, the temperatures may becontrol chamber temperature (T_(CCi)). The value of ΔV_(ri) iscalculated from equation (14). The value of ΔV_(cf)-ΔV_(ci) is thevolume of 6534 and is calculated as

${{\Delta\; V_{cf}} - {\Delta\; V_{ci}}} = {V_{{CC}\mspace{11mu}{Est}}\left\lbrack {1 - \left( \frac{P_{{CC}\mspace{11mu} f}}{P_{{CC}\mspace{11mu} i}} \right)^{1/{nCC}}} \right\rbrack}$

The density of the conduit gas system 6532 before pressure equalizationmay be calculated from an equation similar to (18) that is thevolume-weighted average density for each physical volume (i.e. controlchamber 6510 and interconnecting volumes 6530, 6531):

$\begin{matrix}{\rho_{l\; 0} = \frac{\frac{P_{CCi}\left( {\Delta\; V_{cf}} \right)}{T_{{CC}\mspace{11mu} 0}} + \frac{P_{CC}V_{{IC}\;\_\;{CC}}}{T_{w}} + \frac{P_{Ref}V_{{IC}\;\_\; R}}{T_{w}}}{R\left( {{\Delta\; V_{cf}} + V_{{IC}\;\_\;{CC}} + V_{{IC}\;\_\; R}} \right)}} & (20)\end{matrix}$

The change in the control chamber gas system volume (ΔV_(ct)) used inequation (18) is calculated from the physical volume of the controlchamber 6510 times the quantity one minus the ratio of the final controlchamber pressure over the initial control chamber pressure raised to oneover the polytropic coefficient for the control chamber:

$\begin{matrix}{{\Delta\; V_{cf}} = {{V_{{CC}\mspace{11mu}{Est}}\left\lbrack {1 - \left( \frac{P_{{CC}\mspace{11mu} f}}{P_{{CC}\mspace{11mu} i}} \right)^{1/{nCC}}} \right\rbrack}.}} & (21)\end{matrix}$

An estimate of the control chamber 6510 volume can be derived byassuming constant temperature for the conduit gas system 6532, so thatthe density ratio (ρ_(l 0)/ρ_(l f)) is equal to the pressure ratio(P_(l 0)/P_(l f)). To further simplify the estimate, the polytropiccoefficient is replaced by the specific heat ratio (γ). In this simplerequation, the control chamber 6510 volume is a function of the measuredpressure pairs at the start of pressure equalization (P_(CC 0),P_(Ref 0)) and at the end of equalization (P_(CC f), P_(Ref f)) and thefixed volumes of the reference chamber (V_(Ref)) and interconnectingvolume (V_(IC)):

$\begin{matrix}{V_{{CC}\mspace{11mu}{Est}} = {\frac{{V_{Ref}\left\lbrack {\left( \frac{P_{{Ref}\mspace{11mu} 0}}{P_{{Ref}\mspace{11mu} f}} \right)^{\frac{1}{\gamma}} - 1} \right\rbrack} + {V_{IC}\left( {\frac{P_{{CC}\mspace{11mu} 0}}{P_{{CC}\mspace{11mu} f}} - 1} \right)}}{\left\lbrack {\left( \frac{P_{{CC}\mspace{11mu} f}}{P_{{CC}\mspace{11mu} 0}} \right)^{\frac{1}{\gamma}} - 1} \right\rbrack\left( \frac{P_{{CC}\mspace{11mu} 0}}{P_{{CC}\mspace{11mu} f}} \right)}.}} & (22)\end{matrix}$

The gas in the three closed systems 6512, 6522, 6532 may be modeled asan ideal gas, so the temperature can be determined from the initialconditions and the new pressure or volume:

$\begin{matrix}{T_{i} = {{{T_{0}\left( \frac{p_{0}}{p_{i}} \right)}^{{({n - 1})}/n}\mspace{14mu}{or}\mspace{14mu} T_{i}} = {T_{0}\left( \frac{V_{0}}{V_{i}} \right)}^{n - 1}}} & (23)\end{matrix}$

The initial temperature of the gas in the control chamber (T_(CC 0)) maybe calculated from the temperature of the interconnecting volume walls,the precharge pressure 6316 (FIG. 108A) and the pressures in the controlchamber 6510 just before precharge 6306. The compression of gas in thecontrol volume to the precharge pressure can be modeled as a polytropicprocess and using the ideal gas law in equation (23). The controlchamber 6510 pressure before precharging 6306 is referred herein as thepumping pressure (Ppmp):

$\begin{matrix}{T_{{CC}\mspace{11mu} 0} = {{T_{W}\left( \frac{P_{pmp}}{P_{{CC}\mspace{11mu} 0}} \right)}^{\frac{1}{nCC} - 1}.}} & (24)\end{matrix}$

The temperature of the gas in the control chamber 6510 at the i^(th)step (T_(CC i)) during expansion may be calculated from the initialcontrol chamber 6510 temperature, the precharge pressure 6316 (FIG.108A) and the i^(th) control chamber 6510 pressure (P_(CC i)) usingequation (23):

$\begin{matrix}{T_{{CC}\mspace{11mu} i} = {T_{{CC}\mspace{11mu} 0}\left( \frac{P_{{CC}\mspace{11mu} 0}}{P_{{CC}\mspace{11mu} i}} \right)}^{\frac{1}{nCC} - 1}} & (25)\end{matrix}$

The value of the polytropic coefficient for the control chamber gassystem (nCC) used in equations 14, 17, 19, 21, 25 may vary with thevolume of the control chamber 6510 and range from approximately 1 forsmall volumes to approximately the specific heat ratio for largevolumes. The specific heat ratio for air and other systems ofpredominantly diatomic molecules is 1.4. In one example the value of nCC(for +FMS) can be expressed as a function of the estimated controlchamber volume (eqn 22):nCC=1.4−3.419×10⁻⁵(23.56−V _(CCEst))^(3.074)  (26)

A method to determine a relationship between the volume of the controlchamber (V_(CC)) and its polytropic coefficient (nCC) is described in afollowing section.

Polytropic −FMS Algorithm

A −FMS algorithm similar to the +FMS algorithm, described above, can bedeveloped to calculate the volume of the control chamber 6171 in FIG.105 from the control chamber 6171 and reference chamber 6212 pressuresfor a −FMS process. In the −FMS process the first chamber (e.g. 6171) isprecharged to a pressure below the known second chamber (e.g. 6212).

Referring now to FIG. 109B, the gas in the structures of the controlchamber 6510, the reference chamber 6520 and the manifold lines 6530,6531 can be modeled as three gas masses, 6512, 6532, 6522 that do notmix, but expand, contract, and move through the structures 6510, 6520,6530, 6531. The volume of the control chamber 6510 can be calculatedfrom the measured control chamber 6510 and reference chamber 6520pressures based on thermodynamic models of the three masses 6512, 6522,6532. In the −FMS algorithm, the control chamber mass 6512 is the gasthat occupies the control chamber 6510 at the start of the equalizationprocess. The reference chamber mass 6522 is the gas that occupies thereference chamber 6520 at the end of the equalization process. Themanifold gas 6532 fills the balance of the structure between the controlchamber gas 6512 and the reference chamber gas 6522.

The volume and temperature of the three conceptual closed-systems, 6512,6532, 6522 may then be calculated from initial conditions, pressurepairs, heat transfer assumptions and the constraint of a fixed totalvolume for the 3 closed-systems 6512, 6532, 6522. The pressureequalization can be modeled with a different polytropic coefficient foreach volume 6510, 6520, 6530, 6531 to capture the relative importance ofheat transfer in each. The constant mass, ideal gas and polytropicprocess equations for the three systems, 6512, 6522, 6532 can becombined and arranged to calculate the volume of the control chamber6510. The following paragraphs describe the derivation of one or moresets of equations that allow calculation of the control chamber 6510volume based on pressures measured during the pressure equalization stepof the −FMS process.

Description of Closed Systems for −FMS

The upper image in FIG. 109B presents the positions of the threeclosed-systems 6512, 6522, 6532 at the start of pressure equalization inthe −FMS process. The lower image presents the positions of the threeclosed systems 6512, 6522, 6532 at the end of the pressure equalization.During the equalization process, the locations of the closed systems6512, 6522, 6532 are between the two extremes presented in FIG. 109B. Byway of an example, neither the control chamber system 6512 nor thereference chamber system 6522 fill their respective structures 6510,6520. The following paragraphs present the closed systems in moredetail.

The control chamber gas system 6512 in the −FMS algorithm is the gasthat fills the control chamber 6510 before equalization. The controlchamber gas system 6512 is compressed during pressure equalization asthe initially higher pressure reference chamber gas system 6522 expandsand pushes the manifold gas system 6532 into the control chamber 6510.The control chamber gas system 6512 may modeled with a polytropiccompression during pressure equalization of the −FMS process, where thepressure and the volume are related by:p ₀ V _(CC) ^(nCC)=constant

where p₀ is the initial pressure in the control chamber 6510, V_(CC) isthe volume of the control chamber 6510, and nCC is the polytropiccoefficient for the control chamber 6510.

The reference gas system 6522 in the −FMS algorithm is the gas thatoccupies the entire reference volume 6520 after equalization. Thereference gas system 6522 expands during equalization as the higherpressure gas in the reference chamber 6520 pushes the manifold gassystem 6532 out of the reference chamber 6520 and toward the controlchamber 6510. In one example shown in FIG. 93, the reference chambers(labeled 174 in FIG. 93) are sufficiently open or devoid of interiorfeatures/elements that compression or expansion processes duringpressure equalization may be modeled as adiabatic, so the polytropiccoefficient (nR) may be set equal to approximately the specific heatratio of the gas present in the chamber. The pressure and the volume ofthe reference chamber gas 6522 are related by:p _(R0) V _(Ref) ^(nR)=constant

where p_(R0) is the initial reference chamber 6520 pressure, V_(Ref) isthe volume of the reference chamber 6520, and nR is the specific heatratio for the reference chamber (nR=1.4 air). In another example, wherethe reference chamber 6520 is filled with a heat absorbing material suchas open cell foam, wire mesh, particles, etc that provides for anear-isothermal expansion, the polytropic coefficient for the referencechamber (nR) may have a value of approximately 1.0.

In the −FMS process, the conduit or manifold gas system 6532 occupiesall of the volume of the interconnecting volume 6530, 6531 and afraction 6536 of the reference chamber 6520 before equalization. Afterequalization, the conduit gas system 6532 occupies the interconnectingvolume 6530, 6531 and a fraction 6534 of the control chamber 6510. Theportion of the conduit gas system 6532 that exists in interconnectingvolume 6530 on the control chamber side of the valve 6540 is hereinlabeled as 6533. The portion of the conduit gas system 6532 that exitsin the interconnecting volume 6531 on the reference chamber side of thevalve 6540 is referred to as 6535. The portion of the conduit gas system6532 that exists in the control chamber 6510 is herein labeled as 6534.The portion of the conduit gas system 6532 that exists in the referencechamber 6 520 is referred to as 6536.

In one example the interconnecting volumes 6530 and 6531 may be narrowpassages that provide high heat transfer that assure the conduit gassystem 6532 in volumes 6530 and 6531 is near the temperature of thesolid boundaries or walls of the passages. The temperature of thestructure surrounding the interconnecting volumes 6530, 6531 or manifoldpassages is herein referred to as the wall temperature (T_(w)). Inanother example, the temperature of the conduit gas system 6532 involumes 6530, 6531 is in part a function of the wall temperature. Theportion of the conduit gas system in the control chamber 6534 may bemodeled with the same temperature as control chamber gas system 6512.The control chamber portion of the conduit gas system 6534 experiencesthe same expansion as the control chamber gas system 6512 and may beconceived of as having the same temperature as the control chamber gassystem 6512. The portion of the lines or manifold gas system in thereference chamber 6536 may be modeled with a temperature that is in parta function of the wall temperature. In another example, the referencechamber portion of the conduit gas system 6536 may be modeled as notinteracting thermally with the boundaries of the reference chamber 6520,so that the temperature of the conduit gas system portion in thereference chamber 6536 is a function of the wall temperature and thereference chamber 6520 pressures.

The equations in this section use the following nomenclature:

-   -   variables    -   γ: specific heat ratio    -   n: polytropic coefficient    -   p: pressure    -   V: volume    -   T: temperature    -   superscripts:    -   n: polytropic coefficient    -   nCC: polytropic coefficient for the control chamber    -   nR: polytropic coefficient for the reference chamber    -   subscripts:    -   c: control chamber system    -   CC: physical control chamber    -   f: value at end of equalization    -   i: i^(th) value    -   IC: physical interconnecting volume or manifold passages    -   IC_R: physical interconnecting volume on the reference chamber        side of valve    -   IC_CC: physical interconnecting volume on the control chamber        side of valve    -   l: lines or manifold/interconnecting system    -   0: value at start of equalization    -   pmp: pump    -   r: reference system    -   Ref: physical reference chamber    -   w: wall temperature of interconnecting volume

The equations for the control chamber 6510 may derived from theconceptual model of the three separate mass systems in FIG. 109B and theunderstanding that the total volume of the control chamber mass 6512,reference chamber mass 6522 and interconnecting volumes mass 6532 isfixed. This relationship can be expressed as the sum of the volumechanges of each closed system 6512, 6522, 6532 being zero for eachi^(th) set of values from the start to the end of pressure equalization:

$\begin{matrix}{{0 = {\begin{matrix}{{change}\mspace{14mu}{in}\mspace{14mu}{volume}\mspace{14mu}{of}} \\{{control}\mspace{14mu}{chamber}\mspace{14mu}{mass}}\end{matrix} + \begin{matrix}{{change}\mspace{14mu}{in}\mspace{14mu}{volume}\mspace{14mu}{of}} \\{{interconnecting}\mspace{14mu}{mass}}\end{matrix} + \begin{matrix}{{change}\mspace{14mu}{in}\mspace{14mu}{volume}\mspace{14mu}{of}} \\{{reference}\mspace{14mu}{chamber}\mspace{14mu}{mass}}\end{matrix}}}{0 = {{\Delta\; V_{ci}} + {\Delta\; V_{ri}} + {\Delta\; V_{li}}}}} & (13)\end{matrix}$

where the i^(th) value of ΔV_(ci), ΔV_(ri), ΔV_(li) represents thesevalues at the same point in time. Equations can be developed for thevolume change of the control chamber gas system (ΔV_(ci)), the referencegas system (ΔV_(ri)), and the conduit gas system (ΔV_(li)) based on thepressure/volume relationship of a polytropic process and the ideal gaslaw. The equation for the i^(th) volume change of the control chambergas system 6512 is equal to the i^(th) volume of the control chambermass 6512 less the volume of the control chamber mass 6512 at the startof equalization. The volume of the control chamber mass 6512 at time iis calculated from the volume of the control chamber 6510 times theratio of the final control chamber 6510 pressure over the controlchamber 6510 pressure at time i, raised to one over the polytropiccoefficient for the control chamber 6510:

$\begin{matrix}{{\begin{matrix}{{current}\mspace{14mu}{change}\mspace{14mu}{in}\mspace{14mu}{volume}} \\{{of}\mspace{14mu}{control}\mspace{14mu}{chamber}\mspace{14mu}{mass}}\end{matrix} = {\begin{matrix}{{current}\mspace{14mu}{volume}\mspace{14mu}{of}} \\{{control}\mspace{14mu}{chamber}\mspace{14mu}{mass}}\end{matrix} + \begin{matrix}{{initial}\mspace{14mu}{volume}\mspace{14mu}{of}} \\{{control}\mspace{14mu}{chamber}\mspace{14mu}{mass}}\end{matrix}}}{{\Delta\; V_{ci}} = {{V_{CC}\left( \frac{P_{{CC}\mspace{11mu} 0}}{P_{{CC}\mspace{11mu} i}} \right)}^{1/{nCC}} - V_{CC}}}} & (27)\end{matrix}$

The equation for the reference gas system volume change (ΔV_(r)) isderived from the pressure/volume relationship for a polytropic process.The equation for the i^(th) volume change of the reference chamber gassystem 6522 is equal to the i^(th) volume of the reference chamber mass6522 less the volume of the reference chamber mass 6522 at the start ofequalization. The volume of the reference chamber mass 6522 at time i iscalculated from the structural volume of the reference chamber 6520times the ratio of the initial reference chamber 6520 pressure over thereference chamber 6520 pressure at time i, raised to one over thepolytropic coefficient for the reference chamber 6520:

$\begin{matrix}{{\begin{matrix}{{current}\mspace{14mu}{change}\mspace{14mu}{in}\mspace{14mu}{volume}} \\{{of}\mspace{14mu}{reference}\mspace{14mu}{chamber}\mspace{14mu}{mass}}\end{matrix} = {\begin{matrix}{{current}\mspace{14mu}{volume}\mspace{14mu}{of}} \\{{reference}\mspace{14mu}{chamber}\mspace{14mu}{mass}}\end{matrix} + \begin{matrix}{{initial}\mspace{14mu}{volume}\mspace{14mu}{of}} \\{{reference}\mspace{14mu}{chamber}\mspace{14mu}{mass}}\end{matrix}}}{{\Delta\; V_{ri}} = {{V_{ref}\left( \frac{P_{{Ref}\mspace{11mu} f}}{P_{{Ref}\mspace{11mu} i}} \right)}^{1/{nR}} - {V_{REF}\left( \frac{P_{{Ref}\mspace{11mu} f}}{P_{{Ref}\mspace{11mu} 0}} \right)}^{1/{nR}}}}} & (28)\end{matrix}$

The equation for the volume change of the interconnecting gas system6532 (ΔV_(l)) is derived from the constant mass gas of the system(V*ρ=constant). The equation for the i^(th) volume change of the conduitor manifold gas system 6532 is equal the current volume of the system6532 less the original volume of the system 6532. The current volume ofthe interconnection or manifold gas system 6532 is the initial volumetimes the ratio of initial over current density of the system 6532. Theinitial volume of the interconnecting gas system 6532 is the sum of thevolumes 6534, 6533 and 6535 pictured in FIG. 109B:

$\begin{matrix}{{\begin{matrix}{{current}\mspace{14mu}{change}\mspace{14mu}{in}\mspace{14mu}{volume}} \\{{of}\mspace{14mu}{interconnecting}\mspace{14mu}{mass}}\end{matrix} = {\begin{matrix}{{current}\mspace{14mu}{volume}\mspace{14mu}{of}} \\{{interconnecting}\mspace{14mu}{mass}}\end{matrix} + \begin{matrix}{{initial}\mspace{14mu}{volume}\mspace{14mu}{of}} \\{{interconnecting}\mspace{14mu}{mass}}\end{matrix}}}\mspace{20mu}{{\Delta\; V_{ii}} = {{\left( {{\Delta\; V_{Rf}} + V_{IC}} \right)\frac{\rho_{l\; 0}}{\rho_{li}}} - {\left( {{\Delta\; V_{Rf}} + V_{IC}} \right).}}}} & (29)\end{matrix}$

The density terms ρ_(IO), ρ_(li) are the average density of the gases inthe conduit gas system 6532 at the start of equalization and at somepoint, i, during equalization. The conduit gas system 6532 includesgases as different temperatures and pressures. The conduit gas system6532 includes gas in the volume of the control chamber 6510 in a volumelabeled 6534, gas in manifold passages on the control chamber side ofthe valve 6540 labeled 6533, gas in manifold passages on the referencechamber side of the valve 6540 labeled 6535, and gas in the referencechamber labeled 6536.

These four equations may be combined develop an expression for thevolume (V_(CC)) of the control chamber 6510 as a function of themeasured pressure pairs at the start of pressure equalization (P_(CC 0),P_(Ref 0)), at any point during the equalization (P_(CC i), P_(Ref i)),the reference chamber 6520 pressure at approximately the end ofequalization (P_(Ref f)) and the fixed volumes of the reference chamber(V_(Ref)) and interconnecting volume (V_(IC)):

$\begin{matrix}{V_{CC} = \frac{{V_{Ref}\left\lbrack {\left( \frac{P_{Reff}}{P_{Refi}} \right)^{1/{nR}} - \left( \frac{P_{Reff}}{P_{{Ref}\; 0}} \right)^{1/{nR}}} \right\rbrack} + {\left( {{\Delta\; V_{Rf}} + V_{IC}} \right)\left( {\frac{\rho_{l\; 0}}{\rho_{li}} - 1} \right)}}{\left\lbrack {1 - \left( \frac{P_{{CC}\; 0}}{P_{CCi}} \right)^{1/{nCC}}} \right\rbrack}} & (30)\end{matrix}$

where the densities of the line system 6532 (ρ_(l 0), ρ_(l i)) areevaluated with the initial pressure pairs (P_(CC 0), P_(Ref 0)) and anypressure pair (P_(CC i), P_(Ref i)) during equalization along with theassociated temperatures as described below.

The densities of the conduit gas system (ρ_(l 0), ρ_(l i)) in equations(29) may be calculated from the volume-weighted average density for eachphysical volume (i.e. control chamber 6510, reference chamber 6520, andinterconnecting volumes 6530, 6531):

$\begin{matrix}{{\rho_{li} = \frac{{- {\rho_{CCi}\left( {\Delta\; V_{cf}} \right)}} + {\rho_{{IC}_{CC}}V_{{IC}_{CC}}} + {\rho_{{IC}_{R}}V_{{IC}_{R}}} + {\rho_{ri}\Delta\; V_{ri}}}{\left( {{\Delta\; V_{cf}} + V_{{IC}\_{CC}} + V_{{IC}\_ R} + {\Delta\; V_{ri}}} \right)}}{\rho_{CCi} = {\frac{P_{CCi}}{{RT}_{CCi}} = {{density}\mspace{14mu}{of}\mspace{14mu}{gas}\mspace{14mu}{in}\mspace{14mu}{control}\mspace{14mu}{chamber}}}}{\rho_{{IC}\_{CCi}} = {\frac{P_{CCi}}{{RT}_{{IC}\_{CC}}} = \begin{matrix}{{density}\mspace{14mu}{of}\mspace{14mu}{gas}\mspace{14mu}{in}\mspace{14mu}{manifold}\mspace{14mu}{line}} \\{{on}\mspace{14mu}{control}\mspace{14mu}{chamber}\mspace{14mu}{side}\mspace{14mu}{of}\mspace{14mu}{valve}}\end{matrix}}}{\rho_{{IC}\_{Ri}} = {\frac{P_{Refi}}{{RT}_{{IC}\_{CC}}} = \begin{matrix}{{density}\mspace{14mu}{of}\mspace{14mu}{gas}\mspace{14mu}{in}\mspace{14mu}{manifold}\mspace{14mu}{line}} \\{{on}\mspace{14mu}{reference}\mspace{14mu}{chamber}\mspace{14mu}{side}\mspace{14mu}{of}\mspace{14mu}{valve}}\end{matrix}}}{\rho_{ri} = {\frac{P_{Refi}}{{RT}_{lr}} = \begin{matrix}{{density}\mspace{14mu}{of}\mspace{14mu}{gas}\mspace{14mu}{in}} \\{{reference}\mspace{14mu}{chamber}}\end{matrix}}}} & (31)\end{matrix}$

where R is the universal gas constant for air, the temperatures,T_(IC_CC), T_(IC_R), T_(lc), may be functions in part of the temperatureof the interconnecting volume walls. In another example, thetemperatures, T_(IC_CC), T_(IC_R), T_(lcr), may be functions in part ofthe temperature of the interconnecting volume walls and the gastemperature of the reference chamber (T_(Ref i)). In another example,the temperatures, T_(IC_CC), T_(IC_R), T_(lc), may be theinterconnecting wall temperature (T_(w)). In another example, thetemperatures may be reference chamber temperature (T_(Ref i)).

The value of ΔV_(cf) for equation (31) is calculated from equation (27),where the final control chamber pressure (P_(CCf)) is used for P_(CCi)and V_(CC Est) is used for V_(CC).

The value of ΔV_(ri) for equation (31) is calculated from equation (28).

The density of the conduit gas system 6532 before pressure equalizationmay be calculated from a equation similar to equation (31) that is thevolume-weighted average density for each physical volume (i.e. controlchamber 6510 and interconnecting volumes 6530, 6531):

$\begin{matrix}{\rho_{l\; 0} = \frac{\frac{P_{{ref}\; 0}\left( {\Delta\; V_{rf}} \right)}{T_{W}} + \frac{P_{CC}V_{{IC}\_{CC}}}{T_{W}} + \frac{P_{Ref}V_{{IC}\_ R}}{T_{W}}}{R\left( {{\Delta\; V_{rf}} + V_{{IC}\_{CC}} + V_{{IC}\_ R}} \right)}} & (32)\end{matrix}$

An estimate of the control chamber 6510 volume can be derived byassuming constant temperature for the conduit or manifold gas system6532, so that the density ratio (ρ_(l 0)/ρ_(l f)) is equal to thepressure ratio (P_(l 0)/P_(l f)). To further simplify the estimate, thepolytropic coefficient is replaced by the specific heat ratio (γ). Inthis simpler equation, the volume of the control chamber (V_(CC)) in the−FMS process can be expressed as a function of three pressures [i.e. themeasured pressure pair at the start of pressure equalization (P_(CC 0),P_(Ref 0)), and a single equalization pressure (P_(f))], as well as thefixed volumes of the reference chamber (V_(Ref)) and interconnectingvolume (V_(IC)), and the polytropic coefficients for the referencechamber (nR) and control chamber (nCC):

$\begin{matrix}{V_{CCEst} = {\frac{{V_{Ref}\left\lbrack {1 - \left( \frac{P_{f}}{P_{{Ref}\; 0}} \right)^{1/\gamma}} \right\rbrack} + {\left( {{\Delta\; V_{Rf}} + V_{IC}} \right)\left( {\frac{P_{{CC}\; 0}}{P_{f}} - 1} \right)}}{\left\lbrack {1 - \left( \frac{P_{{CC}\; 0}}{P_{f}} \right)^{1/\gamma}} \right\rbrack}.}} & (33)\end{matrix}$

The gas in the three closed systems 6512, 6522, 6532 may be modeled asan ideal gas, so the temperature can be determined from the initialconditions and the new pressure or volume:

$\begin{matrix}{T_{i} = {{{T_{0}\left( \frac{p_{0}}{p_{i}} \right)}^{{({n - 1})}/n}\mspace{14mu}{or}\mspace{14mu} T_{i}} = {T_{0}\left( \frac{V_{0}}{V_{i}} \right)}^{n - 1}}} & (23)\end{matrix}$

The initial temperature of the gas in the control chamber (T_(CC 0)) maybe calculated from the temperature of the interconnecting volume walls,the precharge pressure 6316 (FIG. 108B) and the pressures in the controlchamber 6510 just before precharge 6306 (see FIG. 108B) modeling it aspolytropic process and using the ideal gas law in equation (23). Thecontrol chamber pressure before precharging 6306 is referred herein asthe pumping pressure (Ppmp):

$\begin{matrix}{T_{{CC}\; 0} = {T_{W}\left( \frac{p_{pmp}}{P_{{CC}\; 0}} \right)}^{\frac{1}{nCC} - 1}} & (24)\end{matrix}$

The value of the polytropic coefficient for the control chamber gassystem (nCC) may vary with the volume of the control chamber 6510 andrange from approximately 1 for small volumes to approximately thespecific heat ratio for large volumes. The specific heat ratio for airand other systems of predominantly diatomic molecules is 1.4. In oneexample the value of nCC for −FMS can be expressed as a function of theestimated control chamber volume (equation 21):nCC=1.507−1.5512×10⁻⁵(23.56−V _(CC Est))^(3.4255)  (34)A method to determine a relationship between the volume of the controlchamber (V_(CC)) and its polytropic coefficient (nCC) is described in afollowing section.Determining the Polytropic Coefficient n_(CC)

The value of polytropic coefficient n_(CC) may be determinedexperimentally or analytically. In possible understanding, thepolytropic coefficient compares the potential temperature change of thegas due to heat transfer with the structure to temperature change causedby pressure changes. The value of the polytropic coefficient may varywith the pressure changes, the rate of pressure changes and the shapeand size of the gas volume.

In one embodiment, the polytropic coefficient n_(CC) is determinedexperimentally by creating control chamber 6171 (FIG. 105) with a knownvolume and executing the +FMS process or the −FMS processes andrecording the control chamber and reference chamber pressures duringequalization. The polytropic +FMS algorithm comprising eqns (17), (18),(20) is applied to the set of pressure measurements and the knowncontrol chamber volume (V_(CC)) in order to solve for the value of thepolytropic coefficient for the control chamber (n_(CC)). This process todetermine the polytropic coefficient was repeated for several differentvolumes ranging 1.28 ml, which is the typical of the control chamber6171 after a fill stroke to 23.56 ml which is typical of the controlchamber 6171 after a deliver stroke. The FMS process may be repeatedseveral times for each volume to improve the accuracy of thedetermination of n_(CC). One example of this experimental determinationn_(CC) for +FMS process is shown in FIG. 110A, where the value of n_(CC)is plotted versed the estimated volume of the control chamber(V_(CC Est)) as calculated by eqn (22) for six different volumes. Apower equation was fit to the data to produce eqn (26) which expressesthe polytropic coefficient in terms of the estimated volume controlchamber. The plot in FIG. 110A plots the value, 1.4-n_(CC), vs.23.56-V_(CC Est) in order to better fit the data with simple equation.

In a similar fashion, the poltytropic coefficient (n_(CC)) for −FMS maybe determined by applying the −FMS process to a known control chambervolume and recording the control chamber and reference chamber pressuresduring equalization. The polytropic −FMS algorithm comprising eqns (30),(31), (32) is applied to the set of pressure measurements and the knowncontrol chamber volume (V_(CC)) in order to solve for the value of thepolytropic coefficient for the control chamber (n_(CC)). This process todetermine the polytropic coefficient was repeated for several differentvolumes. An example of the resulting values for n_(CC) for the −FMSprocess is shown in FIG. 110B, where the value of n_(CC) is plottedversed the estimated volume of the control chamber (V_(CC Est)) ascalculated by eqn (33) for six different volumes. A power equation wasfit to the data to produce eqn (34) which expresses the polytropiccoefficient (n_(CC)) in terms of the estimated volume control chamber(V_(CC Est)). The plot in FIG. 110B plots the value, 1.507-n_(CC), vs.23.56-V_(CC Est) in order to better fit the data with simple equation.

In one embodiment, the fixed known control chamber volume is created byattaching a machined volume to the front of the mounting plate 170 (FIG.92), so that machined volume is sealed to the mounting plate and coversthe ports 173C connecting the control chamber to pressure source andpressure sensor.

Polytropic FMS Calculation Procedure for V_(CC)

Referring now for FIGS. 111 and 112 that present flowcharts to calculatethe volume of the control chamber from the pressure data recorded duringan 2-chamber FMS process and the polytropic FMS algorithm. The flowchartin FIG. 111 presents a relatively simple process that requires a minimumof pressure data to calculate the volume of the control chamber(V_(CC)). The flowchart in FIG. 112 describes a more complex calculationto more accurately calculate the volume of the control chamber (V_(CC))that requires multiple pressure pairs during the equalization process.

The simple polytropic FMS calculation procedure presented in FIG. 111 isexecuted by a processor or controller and starts with step 6400 thatcomprises completing either the +FMS or −FMS process described above andstoring in memory multiple pressure pairs that were recorded during theequalization process. In step 6614, the controller analyzes the multiplepressure pairs to identify the initial control chamber pressure(P_(CC 0)) and the initial reference pressure (P_(Ref 0)) as the controlchamber and reference pressures when the equalization process starts.Methods or procedures to identify the start of equalization or theinitial pressures are described in a previous section titled Pump VolumeDelivery Measurement, where the initial control chamber and referencechamber pressures are referred to as Pd and Pr. In step 6618, thecontroller analyzes the multiple pressure pairs to identify the finalcontrol chamber pressure (P_(CC f)) and the final reference pressure(P_(Ref f)) when the control chamber and reference chamber pressureshave nearly equalized or are changing at a sufficient low rate. One ormore methods to identify when the control chamber and reference chamberpressures have nearly equalized are described in a previous sectiontitled Pump Volume Delivery Measurement.

Alternatively, steps 6614 and 6618 to identify the initial and finalpressures for the control chamber and reference chamber may occur duringthe FMS process 6400. The controller or FPGA processor may identify theinitial and final pressures and store only those values. In one example,the initial pressures could be the control chamber and referencepressures, when the connection valve opens and the final pressures couldthe control chamber and reference pressures when the second valve opensto vent the reference and control chambers after equalization.

In step 6620, the volume of the control chamber is estimated from theinitial and final pressures using either eqn (22) for a +FMS process oreqn (34) for a −FMS process. In step 6641, for a +FMS process, theresulting estimate of the control chamber volume (V_(CC Est)) is thenused in eqns (26) to calculate the polytropic coefficient for thecontrol chamber (n_(CC)). This polytropic value (n_(CC)) and theestimated volume (V_(CC Est)) along with initial and final pressurepairs are supplied to eqns (17), (18), (19) for a +FMS process tocalculated the control chamber volume (V_(CC)). In step 6641 for a −FMSprocess, the polytropic coefficient (n_(CC)) is calculated with eqn 34and the control chamber volume (V_(CC)) is calculated with eqns. (30),(31), (32).

A processor such as controller 61100 in FIG. 105, may perform steps6614-6618 (FIG. 111) on the stored pressure pairs. In an alternativeembodiment, a processor 61100 may perform steps 6614 and 6618 during thepressure equalization without storing the pressure pair

A more complex calculation of the control chamber volume (V_(CC)) isdescribed in FIG. 112. The initial steps of completing the FMS 6400,identifying the initial control chamber pressure (P_(CC 0)) and initialreference chamber pressure (P_(Ref 0)) 6614, identifying the finalcontrol chamber pressure (P_(CC f)) and final reference chamber pressure(P_(Ref f)) 6618, and estimating the control chamber volume (V_(CC Est))6620 are the same as described above for FIG. 111.

The steps 6624, 6628, 6630 and 6640 are similar to the calculation stepsdescribed above in the section titled Pump Volume Delivery Measurement,except that the calculation of the control chamber volume (V_(CC)) isbased on eqns. (17), (18), (19) for a +FMS process and eqns. (30), (31),(32) for a −FMS process. In step 6624, the pressure pairs of the controlchamber pressure (P_(CC i)) and reference chamber pressure (P_(r i)) arecorrected by interpolations with previous subsequent pressure pairs tocalculate pressures pairs (P_(CC i)*, P_(r i)*) that occurred at exactlythe same time. In other embodiments step 6624 is skipped and subsequentcalculations use the uncorrected pressure pair (P_(CC i), P_(r i)). Instep 6628, a control chamber volume (V_(CC)) is calculated for eachpressure pair. In steps 6630, 6640, the optimization algorithm describedin the section titled Pump Volume Delivery Measurement is carried to outidentify the optimal final pressure pair (P_(CC f), P_(Ref f)) and theresulting control chamber volume (V_(CC)).

In an alternative embodiment, the calculations described FIGS. 111, 112may be carried out in a processor that is separate from the controller61100 in FIG. 105. The calculations may for example be carried out inthe FPGA that also handles the input and output signals to and from theactuators, valves and pressure sensors.

Air Detection with the Polytropic FMS Algorithm

Referring now to FIG. 103, another aspect of the invention involves thedetermination of a presence of air in the pump chamber 181, and ifpresent, a volume of air present. Such a determination can be important,e.g., to help ensure that a priming sequence is adequately performed toremove air from the cassette 24 and/or to help ensure that air is notdelivered to the patient. In certain embodiments, for example, whendelivering fluid to the patient through the lower opening 187 at thebottom of the pump chamber 181, air or other gas that is trapped in thepump chamber may tend to remain in the pump chamber 181 and will beinhibited from being pumped to the patient unless the volume of the gasis larger than the volume of the effective dead space of pump chamber181. As discussed below, the volume of the air or other gas contained inpump chambers 181 can be determined in accordance with aspects of thepresent invention and the gas can be purged from pump chamber 181 beforethe volume of the gas is larger than the volume of the effective deadspace of pump chamber 181.

A determination of an amount of air in the pump chamber 181 may be madeat the end of a fill stroke, and thus, may be performed withoutinterrupting a pumping process. For example, at the end of a fill strokeduring which the membrane 15 and the pump control region 1482 are drawnaway from the cassette 24 such that the membrane 15/region 1482 arebrought into contact with the wall of the control chamber 172. A +FMSprocedure as described in FIG. 107 may be carried out to measure thepressure equalization and calculate the apparent volume of the controlchamber 171 (FIG. 11) as described above. However, the +FMS procedureafter a fill stroke, provided that the membrane is off the spacers 50,will also measure the volume of any gas or air bubbles on the liquidside of the membrane 15.

The volume of the control chamber when the membrane 15 is against thecontrol chamber wall 172 is generally a known value based on the designand manufacturing process. This minimum control chamber volume isV_(CC Fix). The control chamber volume measured during a +FMS procedureat the end of a fill command is V_(CC+). If the measured control chambervolume (V_(CC+)) is greater than V_(CC Fix), then the control system 66or controller 1100 may command a −FMS procedure that calculates acontrol chamber volume (V_(CC−)). If the −FMS procedure givessubstantially the same control chamber volume as the +FMS, then thecontroller may recognize that the fill line is occluded. Alternativelyif the −FMS procedure produces a smaller control chamber volume, thenthe controller recognizes the difference as the size of the sum of theair bubbles (V_(AB)):V _(AB) =V _(CC+) −V _(CC−)  (30)

A similar method may be used at the end of the deliver stroke, when themembrane 15 is against the spacers 50. A +FMS procedure will not measurethe volume of air in the liquid, but only the volume of air in thecontrol chamber 171, when the membrane 15 is against the spacers 50.However, a −FMS procedure will pull the membrane away from the spacers50 and will measure the volume of air on the dry side (i.e. controlchamber 171) and the liquid side (pump chamber 181) of the membrane 15.Therefore for the air volume in the liquid (V_(AB)) can also bedetermined at the end of the deliver stroke:V _(AB) =V _(CC−) −V _(CC+)  (31)

Air Calibration

A further aspect of this disclosure includes a method to calibrate the−FMS process and +FMS process with direct measurements of the controlchamber volume 6171 (FIG. 105) using pressure measurements independentof the pressure measurements associated with an FMS process. This methodto calibrate the 2-chamber FMS processes is herein referred to as theAir Cal method. The hardware references in this section will be directedto FIG. 105, but apply equally to the equivalent hardware componentsother pneumatically actuated diaphragm pumps. The Air Cal methodprovides a number of benefits including but not limited to: improvingthe accuracy of the 2-chamber FMS method over the full range of controlchamber volumes; allowing the use of nominal volumes for the referencechamber (V_(Ref)) 6212 and the volume of the interconnecting volumes(V_(IC)) 6204, 6205, 6207, 6209. The method also allows for compensationof differences between the actual and nominal volumes of the referencechamber 6212 and the interconnecting volumes 6204, 6205, 6207, 6209. Themethod also allows for compensation of differences between the actualand the assumed heat transfer in the different volumes of the 2-chamberFMS hardware including the control chamber 6171, reference chamber 6212and the interconnecting volumes, 6204, 6205, 6207, 6209.

The Air Cal method combines control chamber 6171 pressure measurementswith a measurement of displaced fluid to measure the volume of thecontrol chamber 6171 at several membrane 6148 positions between touchingthe control chamber wall 6172 and contacting the spacers 650 on thecassette 624. These measurements of the control chamber volume (VCIso)are compared to the FMS calculated values for the control chambervolumes (VFMS i) to calculate a calibration coefficient (CCal i) foreach calculated FMS volume (VFMS i). A calibration equation can then befitted to a plot of the CCal i values versus the VFMS i values. Thecalibration equation may then be used to improve the accuracy of thecontrol chamber volume calculations. The Air Cal method may be appliedto both the +FMS and −FMS processes and may result in separatecalibration equations for each.

Air Calibration for +FMS

The flow chart 6700 in FIG. 113 describes an example of the Air Calmethod. The hardware setup for the Air Cal includes a pneumaticallydriven pump that is primed with liquid and the outlet plumbed to a massscale (labeled liquid outlet 6191 in FIG. 105) or graduated cylinder.The hardware setup also includes 2-chamber FMS hardware such as acontrol volume or chamber 6171, pressure sensors 6222, 6224, a number ofvalves 6214, 6220 and a reference volume or chamber 6212. A controller61100 to command the pneumatic valves 6214, 6220, record the pressuresfrom the pressure sensors 6222, 6224 and perform the 2-chamber FMSprocedure and calculations is also included.

One example of the hardware setup is the combination of the cassette 24and the APD cycler 14 in which it is installed shown in FIG. 10. In thisexample, the output of the cassette 24 would be plumbed to a mass scale,graduated cylinder, or other fluid measuring apparatus.

Referring back to FIG. 113 and the hardware references in FIG. 105, thefirst step, 6705, primes the pump or cassette 624 and output lines withliquid. The prime also fills the pump chamber 6181 with fluid.

As indicated by the bracket for cycle 6710, the procedure cycles throughsteps 6715 through 6740 several times during the Air Cal method. Thefirst step of Air Cal cycle 6710 completes a +FMS process 6715 thatproduces a provisional measurement of the control chamber volume (VFMSi) for i=1. The Air Cal procedure applies equally to other volumemeasurement techniques which may alternatively be used step 6715. Instep 6720, the pressure in the control chamber 6171 is increased toapproximately P1 by controlling first valve 6220 and holding the gas fora period of time to allow the gas to come into thermal equilibrium withthe chamber walls 6172, and the gasket 6148. In one example, thepressure is held at P1 for 15 to 30 seconds. In another example, thepressure is raised to P1, the pneumatic valve 6220 is closed and the gasin the control chamber 6171 comes to thermal equilibrium with the walls6172, 6148. The control chamber 6171 is isolated by closing valves 6220and 6214. The pressure at the end of step 6720 is recorded at P1 i.

In step 6725, a hydraulic valve 6190 in cassette 624 is released oropened, which allows the pressure in the control chamber 6171 to pushfluid through hydraulic valve 6190 and onto the mass scale (labeledliquid outlet 6191 in FIG. 105). In step 6730 the hydraulic valve 6190is held open long enough for the gas or air in the control chamber 6171to reach pressure equilibrium with liquid on the pump side 6181 (whichhappens quickly) and to come to thermal equilibrium with the controlchamber walls 6172, 6148 (which may take several seconds). In oneexample, the hydraulic valve 6190 is held open for 15 to 30 seconds. Instep 6735, the pressure in the control chamber 6171 is recorded at P2 iand the change in the mass scale is recorded at M_(i). The hydraulicvalve 6190 is then closed.

In step 6740, the calibration coefficient (CCal) is calculated from thefirst and second pressures (P1 i, P2 i) and the displaced liquid mass(M_(i)):

$\begin{matrix}{C_{Cali} = \frac{V_{CIsoi}}{V_{FMSi}}} & (35)\end{matrix}$

where V_(CIso i) is the isothermal determined volume of the controlchamber at the i^(th) position:

$\begin{matrix}{V_{CIsoi} = {M_{i}*\rho\frac{P_{2i}/P_{1i}}{1 - {P_{2i}/P_{1i}}}}} & (36)\end{matrix}$

where ρ is the density of the liquid in the cassette 624 and whereV_(FMS i) is calculated per eqns (17), (18), (19) for a +FMS process.

Cycle 6710 may be repeated multiple times until the membrane 6148reaches the far side of the pump volume or chamber 6181 and contacts thespacers 650. In step 6745, an equation for the calibration coefficientas a function of the FMS determined volume CCal(VFMS) is fit to thedata. The output of the FMS calculations for the volume of the controlchamber 6171 described in the previous section scan now be corrected toobtain a more accurate measure of the control chamber 6171 volume forall possible volumes:V _(CC) =V _(FMS) ·C _(cal)(V _(FMS))  (37)

Air Calibration for −FMS

A calibration coefficient can also be obtained for the −FMS process bythe Air Cal procedure described in FIG. 113. In the −FMS Air Cal method,the pump chamber 6181 and the fluid line to the scale (e.g. liquidoutlet 6191) are primed (step 6705) and the container on the scale ispartial filled with liquid. A −FMS process is completed in step 6715resulting in a −FMS measurement of the control chamber 6171 volume (VFMSi) using and eqns (30), (31), (32). In step 6720, the control chamber6171 pressure is charged to a pressure P1 that is well below the ambientpressure. In step 6725, the low pressure in the control chamber 6171draws fluid into the pump chamber 6181 and out of the container on themass scale. Steps 6730 through 6745 are the same as described above forthe +FMS Air Cal procedure. The resulting equation for the calibrationcoefficient as a function of the −FMS calculated volume CCal(VFMS) maybe applied to −FMS results.

Improved Air Calibration

The accuracy of the V_(CISO i) values may be further increased byconsidering the V_(CISO i−1) and V_(CISO i+1) values. The proceduredescribed in FIG. 113, determines the control chamber 6171 volumessequentially, which may cause their values to be related. Thus value ofV_(CISO i) may be expected to smoothly change from the ith−1 to thei^(th) to the ith+1 position and so on. This dependence on nearbyresults is especially useful at the maximum and minimum values, whichare harder to accurately measure due to the small volume of liquid movedby the pumps. The value of any control chamber volume (VCIso i) can beexpressed by two other independent measurements including the previouscontrol chamber volume (V_(CIso i−1)) plus the displaced liquid volume,the following control chamber volume (V_(CIso i+1)) minus the displacedliquid volume:V _(CIso i) =V _(CIso i−1) +ρ·m _(i−1) =V _(CIso i) =V _(CIso i+1) −ρ·m_(i+1)

Thus the values of VCIso can be improved by averaging them with theadjoining values and the displaced volumes (ρ·m_(i−1)):

$\begin{matrix}{V_{{CIsoi},1} = {\frac{1}{3}\left( {V_{{CIsoi} - 1} + {\rho \cdot m_{i - 1}} + V_{CIsoi} + V_{{CIsoi} + 1} - {\rho \cdot m_{i + 1}}} \right)}} & (38)\end{matrix}$

The resulting averaged values V_(CIso i,1) can be averaged again byfeeding V_(CIso i,1) into equation (38) on the right side to produceV_(CIso i,2). This iterative averaging process can be continued untilthe values of V_(CIso i) stop changing or converge to a value.

The process is a little different for the first and last volume, asthere are values on only one side. The equation to average the firstV_(CIso 1,1) and last V_(CIso N,1) volumes are:

$\begin{matrix}{V_{{{CIso}\; 1},1} = {\frac{1}{2}\left( {V_{{CIso}\; 1} + V_{{CIso}\; 2} - {\rho \cdot m_{2}}} \right)}} & (39) \\{V_{{{CIso}\; N},1} = {\frac{1}{2}\left( {V_{{CIso}\; N} + V_{{{CIso}\; N} - 1} - {\rho \cdot m_{N - 1}}} \right)}} & (40)\end{matrix}$

Again, the resulting averaged values V_(CIso 1,1) and V_(CIso N,1) canbe fed into the right hand side of equations (39) (40) to calculateV_(CIso 1,2) and V_(CIso N,2). This iterative averaging process can becontinued until the values of V_(CIso 1) and V_(CIso N) stop changing orconverge to a value. In cases, where the initial values of V_(CIso 1)and V_(CIso N) are questionable or known to be unreliable, the initialvalues of V_(CIso 1,2) and V_(CIso N,2) can be set based on their morereliable neighbor values:V _(CIso 1,1)=(V _(CIso 2) −ρ·m ₂)V _(CIso N,1)=(V _(CIso N−1) −ρ·m _(N−1))Then subsequent averaging for V_(CIso 1,2) and V_(CIso N,2) can proceedas above.Substantially Instantaneous or Continuous Flow Rate and StrokeDisplacement Estimation

In some embodiments, the flow rate to or from a pump chamber of adiaphragm pump, and/or the stroke displacement of a pump chamber (i.e.the extent to which the diaphragm has traversed the pump chamber) may beestimated while a pumping stroke is occurring. This may be accomplishedeither during a fluid delivery stroke, or a fluid filling stroke of thediaphragm pump. These estimates may be available during the progressionof a pump stroke once sufficient data is collected for controlleranalysis, the controller then being able to act on continuously updatedpressure information to calculate a cumulative volume of fluid movedinto or out of the pumping chamber. Such real-time information may aidin an early determination of an end of stroke, may reduce the number ofpartial strokes performed, may permit more accurate delivery of smallvolumes or increments of fluid, may more efficiently deliver a precisetarget fluid volume, and may provide for earlier detection of occlusionsand other reduced flow conditions, as well aid in priming of a fluidline, etc. This information may also help to increase fluid throughputthrough a pumping cassette.

Flow rate and stroke displacement or stroke progress estimation during apump stroke may be accomplished by monitoring pressure decay in acontrol chamber while a pump stroke is in progress. Data produced frommonitoring the rate of pressure decay may be used by a controller todetermine fluid flow rate through a pumping chamber. Since pressuredecay during a pump stroke is indicative of a change in volume of thecontrol chamber as the pumping chamber fills with or empties of fluid,monitoring this decay over the course of a pump stroke may allow acontroller to estimate stroke displacement as it occurs.

In embodiments in which an on/off, binary, or “bang-bang” pressurecontroller is used, the pressure controller may need to repeatedlyactuate a valve to connect and disconnect a control chamber to apressure reservoir in order to maintain a desired pressure duringpumping. For example, as fluid is pumped out of a pumping chamber duringa delivery stroke, the volume of the associated control chamber willincrease. This will in turn cause a decay in the pressure of the controlchamber. The process or algorithm can be used either with theapplication of negative pressure to fill the pumping chamber or with theapplication of positive pressure to evacuate fluid from the pumpingchamber. The term ‘pressure decay’ as used herein is meant to refer to adecay in the absolute value of the actual pressure being measured (i.e.,a decrease toward ambient pressure in an applied positive pressure, oran increase toward ambient pressure in an applied negative pressure).Once the pressure in the control chamber falls out of an allowedpressure range, the pressure controller may regulate the control chamberpressure by opening a valve to a pressure reservoir. The allowedpressure range may be within a range of a pressure set point. Thispressure regulation or maintenance may involve connecting the chamber toa suitable pressure source for a period of time sufficient to bring thecontrol chamber pressure approximately to a desired value and/or backwithin the allowed range. The pressure will again decay as more fluid isdelivered to or from the pumping chamber and re-pressurization willagain be needed. This process will continue until the end of the strokeis reached.

The repeated re-pressurization will generate a pressure regulationwaveform that appears substantially saw tooth in nature. An example plotshowing a pressure regulation waveform as described above is depicted inFIG. 114. As shown, the waveform oscillates between a lower pressurethreshold 2312 and an upper pressure threshold 2310. The pressure decays(see data points 2302-2304) as the stroke progresses, fluid moves out ofthe pumping chamber, and the volume of the control chamber changes. Inthe example plot in FIG. 114, the control chamber volume is expanding asfluid is pumped out of the pumping chamber of the diaphragm pump to adestination. An end-of-stroke is indicated when the pressure decaylevels off 2305, at which point an FMS volume determination can beconducted by fixing the chamber volume (i.e., closing inlet and outletfluid valves to the pumping chamber), and equalizing 2332 the chamberpressure with the pressure of a known reference volume.

Each pressure decay may be monitored such that the volume of the controlchamber can be approximately known during the course of a pump stroke.This information may allow a determination of the amount of pump strokedisplacement that has occurred when compared with the initial volume ofthe chamber. The initial volume of the pumping chamber can bedetermined, for example, by performing a pre-stroke FMS measurement.This method generally involves determining the volume of a closedchamber by measuring its change in pressure when brought intocommunication with a reference chamber of known volume and pressure. Thedetermination involves closing fluid inlet an outlet valves of thepumping chamber to ensure a constant volume of the control chamber ofthe pump, and then connecting the control chamber to a referencechamber. The process may be modeled as isothermal or adiabatic,depending on the heat transfer properties and dynamics of the system.The system may also be modeled as a polytropic process to optimizemeasurement accuracy. Other methods of determining the initial volume ofthe control chamber can be used. For example, the controller may beprogrammed to assume that the initial control chamber volume issubstantially the control volume physically measured during manufactureof the chambers of the pumping system. This assumption may be employed,for example, when the controller has computed that a precedingend-of-stroke state was fully reached.

The determination of real-time or continuous volume changes in thecontrol and pumping chambers of a diaphragm pump during a pump stroke issubstantially different from previously disclosed pressure-based volumedeterminations, in that a fluid inlet or outlet valve remains open toallow fluid to continue to flow into or out of the pumping chamber.Additionally a reference chamber of known volume and pressure isunnecessary. To distinguish this process from a controlchamber/reference chamber equalization process (a ‘two-chamber’ FMS),the continuous measurement process here described can more aptly beconsidered a ‘one-chamber’ FMS. Although the pumping chamber remainsopen to an inlet or outlet fluid line, the associated control chamberremains a closed system, which allows for determination of a secondvolume once an initial volume is known. Pressure data is repeatedlysampled while the control volume is isolated from a gas source or sink(i.e., no change in mass in the control volume). Under thesecircumstances, controller calculations based on an algorithm using apolytropic process may provide more accurate results. The method is onlynow feasible, because electronic processors capable of rapid dataacquisition and computation are now available. For example, a high speedapplication specific integrated circuit can be employed, or preferablyan FPGA device can now be dedicated to this task, relieving a mainsystem processor from having to share its computing resources and reduceits efficiency. A sufficiently robust FPGA in some embodiments can bereconfigurable or reprogrammable for the blocks of time needed toperform on-the-fly or real time volume measurements during a pumpstroke, while maintaining some resources for other tasks. Real time oron-the-fly volume measurements may be accomplished by finding the volumeof the control chamber at two points between a closure and an opening ofthe supply valve used to regulate the control or pumping chamberpressure. The volume difference between the two points in time may allowthe controller to estimate a relatively real-time flow rate.

As shown in FIG. 114, a high-speed controller can acquire a series ofpressure data points 2302, 2303, 2304, each of which allows thecontroller to successively compute a chamber volume change associatedwith each point. Assuming that the controller has determined a startingvolume of the control chamber, a change in volume at a subsequentpressure decay point can be computed. An ending volume associated withpoint 2302, for example, may then be used as a starting volume at point2303 in order to calculate the ending volume at point 2303, and so on.

FIG. 115 depicts an example graph 5700 with traces representative ofpressure in a control chamber and estimated pumped volume from thatchamber. The volume estimate trace 5702 is created by sampling pressuredata points on each pressure decay 5708 of the pressure trace 5704. Asdescribed above, the controller may use the pressure difference betweentwo pressure data points to determine a volume displaced in anassociated pumping chamber. The controller may then calculate acumulative volume of fluid moved in or out of the pumping chamber. Asmore and more pressure decay 5708 and re-pressurization events 5706occur, the cumulative volume indicated by the volume estimate trace 5704increases. Since the processor is capable or rapidly sampling andanalyzing the data points, the volume estimate is able to be updatedcontinuously as shown in the example graph 5700. As a result, the volumedelivered to or from the pumping chamber can be accurately estimatedwhile the stroke is in progress. This estimate is generated withouthalting the pumping of fluid and without the use of a reference chamber.

Any number of suitable mathematical methods may be used to model thepressure decay of the control (or pumping) chamber throughout a pumpstroke. But it should be understood that a pressure decay curve at onepoint in the pump stroke may appear quite similar to a pressure decaycurve at another point during the pump stroke, yet represent a differentamount of volume change in the pumping chamber. Programming a controllerto analyze the pressure decay curves during a pump stroke by using apolytropic model may help to resolve these potential differences involume change.

One-chamber FMS—computing real-time or continuous volume changes in thecontrol or pumping chamber using a polytropic model—may be feasible insystems using either binary or variable orifice valves connecting thepump control chamber to a pressure reservoir (positive or negativepressure). Pressure data can be acquired and analyzed during the timethat either type of valve is closed (although this time period is likelymuch shorter when a vari-valve is used). In either case, the pressuredecay during fluid egress (or pressure rise during fluid ingress) can besampled, the volume change computed, and the process repeated to providereal-time volume change data. In the following description, a polytropicmodeling process is applied to a system using binary valves inregulating the pressure in the control or pump chamber. The descriptionapplies to other types of valves and pressure regulation protocols.

In general, a one-chamber FMS protocol can be applied to any gas-driven(e.g., air-driven) diaphragm pump having a fluid pumping chamberseparated from a control chamber by a flexible diaphragm. During a pumpstroke, as fluid either enters or leaves the pumping chamber, thecontrol chamber will be a closed system for at least part of the time asthe the controller regulates the pressure delivered to the controlchamber and diaphragm. A valve connecting the control chamber to apressure source will close once the pressure in the control chamberreaches or exceeds a high threshold value. The valve will open again(either fully or partially) as the pressure decays from fluid movementinto or out of the pumping chamber, creating alternating periods duringthe pump stroke in which the control chamber is closed to air ingress oregress. During these phases in which the control chamber is isolated, achange in pressure reflects a change in the volume of the controlchamber—and therefore the pumping chamber. An initial volume at thebeginning of the pressure decay period must be known from a priormeasurement, or assumed. A terminal volume can then be calculated from ameasured pressure change between the initial and terminal volume. Theterminal volume can then be used as the initial volume for the nextcalculation as the pressure decays further during the control chamberisolation phase. In this way, a controller can rapidly acquire pressurereadings during the pressure decay phases of the pump stroke to computein a nearly continuous manner the change in volume of the pumpingchamber, and can thus estimate an instantaneous fluid flow rate into orout of the pump. The relationship between pressure and volume of a gasin a closed system is governed by a standard equation describing thebehavior of ideal gases, and it may be best to assume a polytropicprocess in the calculation, in which a polytropic coefficient can varybetween 1 and a value representing the heat capacity ratio of the gasused in the pump (adiabatic coefficient for that gas).

A polytropic process is governed by the equation:PV ^(n)=constant

where P=pressure, V=volume, and the polytropic exponent, “n”, is anumber between 1 and γ (γ being 1.4, the coefficient describing anadiabatic system for most gases including air). Since the right handside of the equation is a constant, two consecutive points in time canbe compared. To compare two consecutive points in time, the followingequation may be employed:P _(t) V _(t) ^(n) =P _(t−1) V _(t−1) ^(n)where P_(t) is the pressure at time t, V_(t) is the volume at time t,P_(t−1) is the pressure at time t−1, and V_(t−1) is the volume at timet−1.

Rearranging the equation to solve for V_(t) and simplifying yields thefollowing equations:

$V_{t}^{n} = \frac{P_{t - 1}V_{t - 1}^{n}}{P_{t}}$$V_{t} = \sqrt[n]{\frac{P_{t - 1}V_{t - 1}^{n}}{P_{t}}}$$V_{t} = \frac{P_{t - 1}^{1/n} \times V_{t - 1}^{n/n}}{P_{t}^{1/n}}$$V_{t} = {V_{t - 1}\left( \frac{P_{t - 1}}{P_{t}} \right)}^{1/n}$

As shown in the above equations, the current volume of the chamber,V_(t), can be determined if the volume at the end of the preceding timeinterval has been determined. This volume may then be used to determinestroke displacement if desired. Additionally, by tracking the amount oftime between V_(t) and V_(t−1), it is possible to determine a rate offlow over that time span. An average flow rate over a portion of thepump stroke may be determined by averaging multiple flow ratedeterminations using successively paired pressure data values.Additionally, knowing the starting volume and nominal ending volume ofthe control chamber may provide an independent determination of theamount of time needed to complete the pump stroke. In an example, a datasample set may be acquired every 10 ms and may include 20 data samples.In such embodiments, the amount of time between V_(t) and V_(t−1) willbe 0.5 ms. The preferred data sampling rate will depend, among otherthings, on the expected duration of a pump stroke, the rate of pressuredecay observed by the controller, the degree of measurement error ornoise associated with the pressure signal, and the sampling speed andprocessing capability of the controller (e.g., whether a dedicated FPGAis being used).

In some embodiments, the controller may compute the volume change ateach data point sampled. This has the advantage of minimizing theeffects of heat transfer between measurement points. On the other hand,the signal noise during measurement may yield a less accuratecomputation for the change in actual volume. In another embodiment, theprocessor may sample a set of pressure data points within a time periodin which heat transfer is presumed to be at an acceptable level, and thepressure data set may be filtered or smoothed by the processor before aninitial smoothed pressure measurement and a final smoothed pressuremeasurement is used to compute the final volume at the end of the timeperiod. The effects of signal noise on the accuracy of the measurementcan thus be reduced.

There are time periods during a pumping stroke in which pressure dataacquisition is either not possible or inadvisable. For example, when thepressure supply valve is open and the pump chamber pressure is spiking,fluid flow into or out of the pumping chamber continues. As a firstapproximation, it may be assumed that the fluid flow rate during thisshort period of time remains approximately unchanged from the flow ratemeasured shortly before the opening of the pressure supply valve. Thevolume change estimated in this manner may then be added to the volumerepresenting the last measured pressure data point to arrive at theinitial volume for the next measured pressure data point. Additionally,there may be prescribed points of time during a stroke at which pressuredata points may be ignored. For example, depending on the data samplingrate, pressure information immediately preceding a pressure rise duringa pressurization event may be inaccurate. Some aliasing may also bepresent for data points directly following a pressurization event. In anembodiment, data points collected by the controller within apredetermined period of time before and after a pressurization event maybe discarded or ignored to further improve the accuracy of the flowdetermination process.

In embodiments which use an FPGA for pressure data acquisition andanalysis, issues stemming from an inferior sampling rate may presentless of a concern. In certain embodiments, an FPGA may also have theresource capacity to control the relevant valves in the pumping system.By controlling the pressure supply valves, the FPGA may be able toschedule the sampling of pressure data more efficiently. Synchronizationof events may be improved, and aliasing problems with data sampling maybe reduced.

Certain assumptions may also be made at the beginning of a pump stroke.A small amount of fluid movement into or out of the pumping chamber islikely to be present prior to the first pressure decay event. Althoughinertial forces may limit the initial fluid flow, the controller can beprogrammed to estimate an initial fluid flow and volume change prior tothe first data sampling point during pressure decay. Such an assumptionmay allow for the estimation of changes in chamber volume while pressuredecay information at the beginning of the stroke is not available. Theamount of fluid assumed to have been moved at the start of a stroke maydepend on the pumping pressure applied to the control and pumpingchambers. The controller may be programmed to include a pre-determinedvolume of fluid movement based on the value of the applied pressure.Alternatively, after number of data points have been sampled todetermine an estimated flow rate, the flow rate may be used toextrapolate for the volume moved while the data was unavailable. It may,for example, be assumed that the flow rate over that period of time wassubstantially equal to the currently estimated flow rate. Thisassumption that the flow rate is constant may then be used to determinean estimate of the volume moved over the period which data wasunavailable.

FIG. 116 shows a flowchart detailing an example of a number of stepswhich may be used to estimate control chamber volume changes during apump stroke. As shown, the flowchart begins in step 5200, where apre-stroke FMS measurement is made, which in an embodiment includesfreezing the volume of the pumping and control chambers, measuringcontrol chamber pressures and equalizing pressures with a referencevolume chamber. This measurement may provide a starting control chambervolume measurement. Alternatively, the starting control chamber volumemay be assumed by the controller to be a fixed and known quantity if thecontroller has calculated that the preceding end-of-stroke of thepumping chamber has been fully completed. A pump stroke may then bestarted in step 5202. In step 5204, the control chamber pressure decay(or the decay of the absolute value of the pressure) may be monitored asthe stroke displaces and causes fluid to move into or out of the pumpingchamber. In some specific embodiments, multiple data points may besampled along each decay curve and the mathematical model describedabove may be used to determine changes in control chamber volume as thepump stroke proceeds. Data points and volume information may be saved inmemory 5208.

Assuming the end of stroke is not detected, once the pressure in thecontrol chamber falls outside of a predetermined range (e.g. falls belowa predetermined pressure value), step 5210 may be performed. In step5210, the pressure controller may perform pressure maintenance on thecontrol chamber (i.e. re-pressurize the control chamber) to bring thecontrol chamber pressure back to approximately a preprogrammed desiredvalue (which may, for example, be at or near a high pressure bound ofthe range). After completing step 5210, step 5204 may be repeated withthe collected data again being saved in memory 5208. This may continueuntil an end of stroke condition is detected. (End of stroke detectionis described elsewhere).

In the event an end of stroke condition is detected, a post-stroke FMSmeasurement (determining volume by measuring control gas pressure) maybe taken in step 5212. This measurement may be compared to themeasurement from step 5200 to check and/or more precisely determine thetotal volume moved during the stroke. Additionally, this post-stroke FMSmeasurement may serve as the starting control chamber volume measurementfor the next stroke performed by that pump chamber.

Other means of determining that the pump has fully completed its pumpstroke may be used. If so, the result of that determination may then beused to initialize the controller to the control chamber's startingvolume for the next pump stroke. Methods other than volume determinationby pressure measurement may be used to assess the final volume of thecontrol and pumping chambers, whether or not a pump stroke has beenfully completed. However the final chamber volume is determined, thatvalue may then be used to initialize the controller as the chamber'sstarting volume for the next pump stroke.

The polytropic coefficient, “n”, of the above described mathematicalmodel may be initialized at a specific value. For example, in someembodiments, the coefficient may be set to 1.4 or γ (representing anadiabatic process for air). The initialized value may differ dependingon the embodiment, the type of control fluid, or the intended flow rate.For example, embodiments with a relatively fast flow rate may be moreappropriately modeled as an adiabatic system while embodiments with aslower flow rate may be more appropriately modeled as an isothermalsystem.

The coefficient may then be adjusted to a value yielding greateragreement between the computed real-time flow rate and the measuredfinal volume change at end-of-stroke over a plurality of pump strokes.This may be done by using feedback collected over one or more pumpstrokes using any suitable software algorithm, or using a controllersuch as a proportional controller or PID controller. Feedback may be inthe form of a calculated delivered volume determined by a comparison ofthe pre-stroke and post-stroke FMS measurement. The final FMSmeasurement volume and estimated real-time volume change determinedusing a current value for “n” may be compared. If the volumes differ bymore than a predetermined amount the value for “n” may be adjusted. Thenew coefficient value may then be saved and used as the initial valuefor the next pump stroke. In an example, the coefficient “n” may beadjusted using data collected over several pump strokes. For example,values for “n” that would have yielded the final (e.g. FMS measured)volume moved for a number of strokes may be averaged together. In theabsence of significant changes in ambient conditions (e.g., fluid orenvironmental temperature changes), an averaging or other numericalfiltering procedure may decrease the time needed to produce accurateflow rate and stroke displacement measurements, as it may not benecessary to have the controller perform repeated comparisons ofpre-stroke and post-stroke FMS measurements.

FIG. 117 shows a flowchart outlining an example of a number of steps toadjust the coefficient of the mathematical model as described above. Asshown, in step 5220, a pre-stroke FMS measurement may be taken todetermine a starting volume for a control chamber. The stroke may thenbegin in step 5222. In step 5224, the pressure decay on the pressureregulation waveform may be monitored. Volume change of the controlchamber may be determined using the example mathematical pressure-volumemodel with a predefined initial exponent coefficient value. Once thestroke has completed, in step 5226, a post-stroke FMS measurement may bemade to determine the end of stroke control chamber volume. In step5228, the volume measurements from step 5220 and 5226 may be compared todetermine the total control chamber volume change over the stroke. Thecoefficient may be adjusted based on this comparison to align the twofinal values if necessary. For example, the coefficient may be adjustedto the value which would have yielded the volume change found by usingthe FMS measurements.

As mentioned above, a flow rate estimation as a stroke is progressingmay be used for a number of purposes including, but not limited to,detection of occlusions, detection of low flow or no flow conditions,detection of end of stroke, detection of fluid line prime state, etc.The flow rate estimation may be monitored to determine if it is likelythat an end of stroke condition is present. For example, if thereal-time flow rate drops below a predefined threshold (e.g. 15 mL/min),it may be an indication that a pump stroke has been fully completed(i.e. the maximum volume of fluid has been moved given the physicallimitations of the pump). If the flow rate estimate drops below thepredefined threshold, an FMS measurement may be performed on the chamberand the volume delivered may be verified. If the FMS measurementdetermines the end of stroke has been reached, the chamber may move ontothe next pumping operation (or pump stroke). If an end of strokecondition has not been reached, the controller may undertake a number ofactions, including, for example, attempting to resume the pump stroke.Alternatively, the detection of a reduced flow condition may beindicative of an occlusion of the fluid line, an occlusion alert oralarm may be triggered, or a fluid pushback attempt may be made todetermine if an occlusion exists.

In some embodiments, the controller may be programmed with an armingroutine (a software trigger) to keep it from declaring an end-of-strokecondition prematurely. This may help to avoid false triggering of an endof stroke determination. For example, a lack of cumulative pressure dataat the beginning of a stroke may increase the effect of signal noise ina flow rate determination. In an example, the controller may beprogrammed with a trigger that is armed only after a pre-determined timeperiod has elapsed after the initiation of the pump stroke. In someembodiments the software trigger may be the attainment of apredetermined flow rate value. Or the trigger may be armed after is thecontroller estimates that a predetermined volume of fluid has beenmoved. Requiring that the end of stroke detection trigger be armedbefore an end of stroke condition is detected may help to reduce thenumber of partial strokes performed and may help to increase throughputof fluid through a pumping cassette. To help prevent a scenario in whichthe arming criteria is not reached and the end of stroke is neverdetected, the trigger may be armed after the stroke has been in progressfor a predetermined amount of time. In other embodiments, after apredetermined period of time has elapsed since the beginning of thestroke without the arming criteria being met, and end of stroke mayautomatically be triggered.

FIG. 118 shows a flowchart outlining a number of example steps to detectend of stroke based on a real-time flow rate estimation. As shown, instep 5240, a pre-stroke measurement may be performed to determine thestarting volume of a control chamber. The pump stroke is then started instep 5242. As the stroke progresses, in step 5244, the pressure decay onthe control chamber pressure regulation or maintenance waveform ismonitored. A flow rate is estimated based on the pressure decay. Whenthe end of stroke arming criteria is met, the controller determineswhether the flow rate is above a pre-established or predetermined flowrate. If the flow rate is above the predetermined flow rate, the pumpstroke continues in step 5246 and flow rate estimation continues in step5244. In the event that the flow rate drops below the predetermined flowrate, in step 5248, the stroke may be ended and an end of stroke FMSmeasurement may be made to determine the control chamber volume.

In some embodiments, estimation of control chamber volume change overthe progression of the stroke may be used to predict the amount of timenecessary to complete the stroke. Since the starting volume as well asthe nominal or projected end volume of the stroke is known and flow ratemay be determined using control chamber volume change, the controllermay use this information to estimate how long the entire stroke shouldtake. Correspondingly, the controller can calculate an estimate of howmuch time is needed to complete the remaining portion of the stroke.Once the predicted end time of the stroke is reached, the stroke may bestopped and an FMS measurement may be made. In the event that the FMSmeasurement indicates the stroke was a partial stroke, a number ofactions may be taken. In some embodiments, a cycler may attempt to retrythe stroke. Alternatively, controller detection of a reduced flowcondition may be an indication for an occlusion alert or alarm, or apushback attempt may be made to determine if an end-of-line occlusioncan be relieved.

FIG. 119 shows a flowchart outlining a number of example steps which maybe used to determine end of stroke by predicting time necessary tocomplete a stroke. As shown, in step 5250, a pre-stroke FMS measurementmay be taken to determine the starting volume of a control chamber. Astroke is started in step 5252. When the stroke begins, a stroke timercan be started in step 5254. As the stroke progresses, in step 5256, thepressure decay on the pressure regulation or maintenance waveform forthe control chamber is monitored. This may be used to estimate thecontrol chamber volume and flow rate. These estimates may then be usedin step 5258 to project an estimated stroke time. The estimated stroketime may be calculated by finding the difference between a currentchamber volume and the projected end of stroke chamber volume. Theestimated flow rate may then be used to find the amount of time requiredto complete the stroke. The estimated end-of-stroke time may then becompared to the elapsed stroke time in step 5260. If the estimatedend-of-stroke time is longer than the elapsed stroke time, steps 5256,5258, and 5260 may be repeated. If the estimated end-of-stroke time isless or equal to than the actual elapsed stroke time, the controller maydeclare an end of stroke condition. In step 5262, the stroke is endedand an FMS measurement may be taken to determine the post-stroke volumeof the control chamber. In some embodiments, remaining stroke timeestimations may be made until a predetermined amount of stroke timeremains or a predetermined amount of stroke displacement has occurred.The controller continues the stroke until that time expires and step5262 can then be performed.

The availability of real-time flow rate estimation offered by theexemplary mathematical model described above may allow for earlierdetection of reduced flow conditions as well. Instead of having acontroller wait for a stroke to finish, performing a volume measurementand comparing it to a previous measurement, the controller can beprogrammed to respond to a real-time flow rate that is less than anexpected flow rate threshold. The controller can be programmed to stopthe pump stroke at that point to perform a more precise volumemeasurement (e.g., via an FMS measurement) to verify the flow rateestimate. Thus, reduced flow conditions may be detected without the needto complete prolonged pumping strokes caused by the reduced flow. Thismay save time, reduce patient discomfort, and may help to increaseoverall fluid throughput of a pumping cassette. It may also allow atherapy to transition more quickly from the end of a drain phase to thefill phase of the next cycle. This increased efficiency may allow formore therapy time to be allocated to dwells. In one example, thecontroller may be programmed to declare a reduced flow condition whenthe flow rate estimate is below a threshold of 50 mL/min. In someembodiments, before a reduced flow condition is declared, the flow ratemay have to remain below the threshold for a predefined period of time(e.g. 30 seconds).

Optionally, there may be a plurality of reduced flow conditionclassifications defined by different flow thresholds. For example, inaddition to a low flow threshold (e.g. <50 mL/min) the controller may beprogrammed to recognize a ‘no flow’ threshold which is set lower thanthe low flow threshold (e.g. <15 mL/min).

FIG. 120 shows a flowchart outlining a number of example steps which maybe used to detect a reduced flow condition during a pump stroke. Asshown, in step 5270 a pre-stroke FMS measurement may be taken todetermine the starting volume of a control chamber. A stroke is thenstarted in step 5272. In step 5274, the pressure decay on the pressureregulation or maintenance waveform may be monitored such that real-timecontrol chamber volume change and flow rate may be estimated. Thecontroller continues with the pump stroke as long as the flow rate isgreater than a predetermined flow rate for a predetermined period oftime. The controller continues to monitor the pressure decay waveformsas described in step 5274. If the end of stroke is reached, an end ofstroke FMS measurement may be made in step 5276 to determine the end ofstroke control chamber volume. If is the controller determines that theflow rate is less than the predetermined flow rate for a predeterminedperiod of time, an FMS measurement may be made in step 5278 to confirmthat a reduce flow condition exists. If the reduced flow condition isnot confirmed, the stroke may continue, and the controller continues tocompute flow rate based on the control chamber pressure regulation ormaintenance waveform as described above in step 5274.

If the reduced flow condition is confirmed by the FMS measurement instep 5278, in step 5280 a reduced flow or occlusion notification, alert,or alarm may be sent to the user. This may be done via a user interfaceand may be accompanied by an audible message or tone, vibratoryindication, etc. The response generated by the cycler controller may bedependent on the flow rate detected. Before indicating an occlusion ispresent, a pushback of fluid into the fluid reservoir (or peritonealcavity, depending on the fluid line) may be triggered. In the event thatthe pushback attempt is unsuccessful, the controller may issue anocclusion alert.

In some embodiments, in the event a reduced flow condition is detected,a cycler controller may verify whether or not a target volume for apumping operation (e.g. a drain phase) has been achieved (e.g., acompleted peritoneal drain). If the target volume or more has beenmoved, the controller may declare that the pumping operation has beencompleted. In some embodiments, a device controller may require aminimum defined time period to have elapsed to ensure that the fluidreservoir (e.g., solution bag, heater bag, or a patient's peritoneum) issubstantially empty.

Real-time measurement of fluid flow during a pump stroke can permit thetargeting of specific fluid volume deliveries less than a full pumpstroke volume, or an integer multiple of a full pump stroke volume. Thecontroller may be programmed to end a stroke when the chamber volumechange estimated through pressure measurement indicates that the targetvolume has been delivered or withdrawn. Upon this occurrence, thecontroller may initiate an FMS measurement to confirm that the targetvolume was actually reached. Real-time fluid flow measurement may avoidthe need to perform multiple FMS measurements while repeatedly makingsmall displacement partial strokes to avoid over-shooting the targetvolume. Such a targeting scheme may be particularly desirable in apediatric application in which the amount of time spent approaching butnot over-shooting a target volume would otherwise take a relativelylarge portion of time in a pumping operation.

FIG. 121 shows a flowchart outlining a number of example steps that maybe used to determine when a target volume of fluid has been moved. Asshown, the steps make use of an estimated volume moved based onmeasurement of pressure decay during a stroke to end the stroke when thetarget volume is estimated to have been reached. A pumping operationbegins at step 5290. This operation may, for example, be a fill phasefor a peritoneal dialysis cycle. When the pumping operation begins, anFMS measurement may be made and a pump stroke is started as shown instep 5292. During the stroke, the pressure decay on the pressureregulation or maintenance waveform may be monitored in step 5294. Thisallows for an estimation of volume displacement and flow rate as thestroke progresses. The stroke may end and a post-stroke FMS measurementmay be conducted in step 5296. A cycler controller tracks the computedcumulative volume to see if the difference between the target volume andthe total volume of fluid delivered during the pumping operation isgreater than a full pump chamber volume. If so, the controller proceedsto command the next pump stroke in step 5297. Steps 5294, 5296, and 5297may be repeated until the difference between the target volume and totalvolume pumped is less than the volume of one full pump chamber. At thispoint, in step 5298, if the delivery of another full chamber volumewould cause the target volume to be exceeded, step 5298 is performed.

In step 5298, a targeting trigger may be set as the difference betweenthe total delivered volume for the pumping operation and the targetvolume for the pumping operation. The pump stroke may then proceed instep 5300 until the controller calculates through pressure decaymeasurements that the target volume has been reached. At this point,step 5302 may be performed in which the stroke is ended and an FMSmeasurement may be made to confirm that the target volume of fluid hasbeen moved.

Computing an estimated flow rate from a pressure decay curve during apump stroke may also allow the controller to close a valve or valves ina preemptive manner in order to more precisely deliver a pre-determinedfluid volume. That is, the valve(s) may be closed before the targetvolume is delivered to account for a delay between the controllercommand and the valve's mechanical response. The flow which occursduring the period of time required to physically close the valve (s) maythen cause the target volume to be substantially met. Specifically, thecontroller may estimate the amount of time required to physically toclose the valve(s). In some embodiments, this estimation may be apreprogrammed value. For example, for a particular valve arrangement theresponse delay may be approximately 100 ms. Based on a real timecomputation of the flow rate, the volume of fluid moved during the valveresponse delay can be estimated. This amount of fluid may be subtractedfrom the target volume to yield a valve closure trigger volume. Once thevalve closure trigger volume has been met, the cycler controller cancommand the valves to close.

Fluid Line Prime State Using Estimated Flow Rate and Estimated StrokeDisplacement

In some embodiments, in-stroke computed flow rate and estimated strokedisplacement may be used to determine the prime state of a fluid line.As described above in relation to FIGS. 20-28, a patient line mayinclude a feature (e.g. a restriction such as an orifice) which presentsrelatively little impedance to the flow of air, but a comparatively highdegree of impedance to the flow of a dissimilar fluid, e.g. a liquidsuch as dialysate. The feature may be located proximal to or at theterminal downstream end of the line. The feature may have a flow pathhaving a smaller cross sectional area than that of the fluid conduit inthe main part of the fluid line. When liquid reaches the feature, theflow slows and this will be reflected in the flow rate estimationconducted during the pump stroke (i.e., the pressure decay curve shows ashallower decline). The flow rate may be monitored and when it isdetermined that the flow rate has decreased to a restricted flow rate ordecreased to within a range of the restricted rate, the controller candeclare that fluid in the line has reached the restriction. Strokedisplacement estimation may also be useful in determining whether changein flow rate is due to an end-of-stroke condition or liquid flow beingimpeded by the feature. The impedance feature may be placed near the endof the line such that when it is detected that liquid has reached thefeature, the line may be determined to be primed.

Detecting an impedance change in a line may have other uses. Forexample, a A flow restriction can be used to detect when a fluid flowingpast the restriction changes in composition, density, viscosity, etc. Insuch embodiments, impedance restriction may be placed at a location ofinterest in the conduit. Flow rate through the conduit may be monitoredto detect the change in flow when the composition or fluid of differingproperties or characteristics reaches the restriction.

FIG. 122 shows a flowchart outlining a method to detect that a patientline has been primed by monitoring the slope of a pressure decay curve,computing a flow rate, or estimating a stroke displacement. In theexample flowchart, for illustrative purposes only, deliver strokes aredepicted for the priming of a fluid line. It can be assumed that after achamber has finished its stroke, that chamber performs a fill stroke andis refilled. The flowchart also begins with each chamber in a filledstate.

Priming of the line is begun in step 5330. This may include performing apre-stroke FMS measurement and starting a stroke in step 5332. Step 5334may occur as the stroke is in progress. In step 5334, the pressure decayon the pressure maintenance waveform may be monitored such that a flowrate and stroke displacement computation or estimation may be made. Ifthe flow rate indicates that liquid in the patient line has reached therestriction, the user may be notified, in step 5336, that the line hasbeen primed.

If the flow rate does not indicate that the restriction has beenreached, the stroke may continue until a stroke displacement thresholdhas been reached. Once the stroke displacement estimation indicates thatthe stroke displacement threshold has been reached, the stroke may beended and a post stroke FMS measurement may be made in step 5338. Thestroke displacement threshold may be set so that it is less than thedisplacement necessary to deliver a full chamber volume. Thus, partialstrokes may be purposefully delivered when the patient line is primed.This will ensure that a detected decrease in flow rate is notattributable to an end-of-stroke condition having been reached. Once thepost stroke FMS measurement in step 5338 has finished, the next pumpstroke may begin in step 5340. In a single pump system, the controllercan command a pump-filling operation to re-fill the pumping chamber withfluid. In a dual pump system, the controller can alternatively command asecond pump to begin delivery of fluid from its pump chamber. As shown,after the next stroke begins, the flowchart resets to step 5334. Flowrate and stroke displacement are again estimated during the stroke. Acycler may continue making pump strokes until the flow rate indicatesthat the line has been primed.

FIG. 123 shows a flowchart outlining steps used to detect that a patientline has been primed by computing flow rate. After a chamber hasfinished its stroke, that chamber performs a fill stroke and isrefilled. The steps depicted by the flowchart are assumed to begin witheach chamber in a filled state.

In step 5354, the pressure decay on the pressure regulation ormaintenance waveform may be monitored in order for the controller tocompute a flow rate. When the flow rate is determined to have slowed,the current stroke may be ended and a post stroke FMS measurement may beperformed in step 5356. The next pumping stroke may then begin in step5358. In the example embodiment in FIG. 123, a subsequent pumping strokeat 5358 is delivered from another pumping chamber in a multi-chamberpumping cassette. In step 5360, the pressure decay on the pressuremaintenance waveform may be monitored so that a controller can compute aflow rate during the stroke. If the flow rate estimation at the start ofthis stroke indicates a slow or low flow rate condition, the controllercan declare that the line is primed. Preferably, this determination ismade in a short amount of time so as to minimize the amount of fluidpumped if the line is indeed fully primed. The stroke is ended and anFMS measurement may be made in step 5362. A user may then be notifiedthat the line is primed in step 5364.

In the event that the flow rate is not slow or low, the controller mayconclude that the previous reduction in flow rate was due to anend-of-stroke condition being reached. In this event, the flowchartreturns to step 5354 where stroke continues and the pressure decay onthe pressure maintenance waveform for the control chamber continues tobe monitored. Flow rate estimations continue to be made and the stepsoutlined in the flowchart may repeat as described above until it isdetermined that the line has been primed.

FIG. 124 shows a flowchart outlining steps to detect that a patient linehas been primed by setting a target delivery volume of fluid. Thisvolume may be set to be equal to the nominal interior volume of thepatient line included in the set. A pre-stroke FMS measurement may beperformed and a stroke may be started in step 5372. In step 5374, thepressure decay on the pressure maintenance waveform during a pump strokemay be monitored such that a flow rate estimation and strokedisplacement estimation may be made. In some embodiments, step 5374 maybe optional. Once the stroke has been delivered, the stroke may be endedand a post-stroke FMS measurement may be conducted. If the differencebetween the target volume of fluid and the total volume of fluiddelivered is greater than the full volume of a pump chamber, then step5378 may be performed and the next pumping stroke begins. As shown, step5374 may be repeated while the delivery stroke is in progress.

In the event that after a stroke is completed, the difference betweenthe target volume of fluid and the total volume of fluid delivered isless than the volume of a full pumping chamber, the cycler may proceedwith the next delivery pumping stroke in step 5380. When the estimatedflow rate is observed to have slowed, the controller may declare theline to be primed. The stroke may be ended and an FMS measurement may bemade in step 5384. The user may then be notified in step 5386 that theline has been primed.

In some embodiments, the controller may verify that a line has beenprimed by valving the line to a second pump and commanding the secondpump to begin a pump stroke. If the pressure decay during the secondpump stroke indicates a reduced flow rate similar to that of the firstpump, the controller can declare that the line is indeed primed.

Set Differentiation

In some embodiments, a controller-computed flow rate and estimatedstroke displacement may be used to determine which type of fluid lineset is installed in a cycler (the types of fluid line sets may differ intotal volume due to variations in tubing length, diameter, size andnumber of drip chambers, Y-connections or branches, etc.). Thecontroller can also use the same procedure to cross-check previouslyacquired information about the fluid set. This information may beacquired through a user input via the user interface of the cycler.Additionally, in some embodiments, the controller may acquire thisinformation by using an input device or sensor configured to read a barcode, data matrix or other identification marking.

A preset pumping pressure may be used to pump fluid through the linewhen computing a flow rate for such a determination. A lower flow ratewill indicate a smaller diameter line, or one of greater length. In thismanner, a controller may be able to determine, for example, whether anadult set or a pediatric set (which will have smaller fluid conduit) isinstalled in the medical device. This determination may be made when themedical device is priming the patient line of the set. The medicaldevice may differentiate between sets with different length lines, forexample, by monitoring the amount of volume pumped in order to prime theline. Longer lines (e.g. sets which include an extension) will require alarger priming volume than shorter lines. In some embodiments, flow ratedata and prime volume data may be analyzed together to differentiatebetween set types. Flow rate data and prime volume data may be comparedto a list of expected values from a number of different sets which maybe used in a medical device in order to determine which set is installedin the device.

FIG. 125 shows a flowchart outlining a number of example steps which maybe used by a cycler to differentiate which set of one or more differentsets has been installed in a medical device (such as a peritonealdialysis cycler). In the example embodiment shown in FIG. 125 thisdetermination is made during priming of a line (e.g. the patient line)included in the set. As the line is primed in step 5580, the flow rateduring the prime and the volume delivered to the line during the primeare monitored in steps 5584 and 5582 respectively. As described above, apre-determined pumping pressure may be used to help ensure variations inflow rate between different sets are attributable to the type ofinstalled set.

The medical device may detect the prime status of the line with a primesensor such as any of those described herein. When the prime isfinished, the controller may, in step 5586 compare the flow rate andvolume primed to a stored list of expected values for different setsthat are available to be installed in the medical device. In someembodiments, these expected values may be determined empirically at thetime of manufacture. Optionally, a range of values may be listed foreach of the sets. The set type is identified in step 5588. This may bedone by determining which set type in the list is closest to theobserved flow rate and prime volume values during the prime. If the settype identified in step 5588 does not match previously collected dataabout the set, the controller may notify the user. This notification mayinclude a visual notification on a user interface and may also beaccompanied by an audio tone or alert.

Additionally, if other data has been collected about the set (e.g. froma marking or indicia on the set or from a therapy program) it may beused to verify set type identified in step 5588 is an expected set type.In the event that the set type identified in step 5588 is inconsistentwith other previously collect set related data, step 5589 may beperformed and the controller may generate a notification for the user.

Head Height Detection

In some circumstances, it may be useful to determine the heightwiselocation of the patient relative to the cassette 24 or other portion ofthe system. For example, dialysis patients in some circumstances cansense a “tugging” or other motion due to fluid flowing into or out ofthe patient's peritoneal cavity during a fill or drain operation. Toreduce this sensation, the cycler 14 may reduce the pressure applied tothe patient line 34 during fill and/or drain operations. However, tosuitably set the pressure for the patient line 34, the cycler 14 maydetermine the height of the patient relative to the cycler 14, theheater bag 22, drain or other portion of the system. For example, whenperforming a fill operation, if the patient's peritoneal cavity islocated 5 feet above the heater bag 22 or the cassette 24, the cycler 14may need to use a higher pressure in the patient line 34 to deliverdialysate than if the patient's peritoneal cavity is located 5 ft belowthe cycler 14. The pressure may be adjusted, for example, by alternatelyopening and closing a binary pneumatic source valve for variable timeintervals to achieve the desired target pump chamber pressure. Anaverage desired target pressure can be maintained, for example, byadjusting the time intervals to keep the valve open when the pumpchamber pressure is below the target pressure by a specified amount, andto keep the valve closed when the pump chamber pressure is above thetarget pressure by a specified amount. Any adjustments to maintain thedelivery of a complete stroke volume can be made by adjusting the filland/or delivery times of the pump chamber. If a variable orifice sourcevalve is used, the target pump chamber pressure can be reached byvarying the orifice of the source valve in addition to timing theintervals during which the valve is opened and closed. To adjust forpatient position, the cycler 14 may momentarily stop pumping of fluid,leaving the patient line 34 in open fluid communication with one or morepump chambers 181 in the cassette (e.g., by opening suitable valve portsin the cassette 24). However, other fluid lines may be closed, such asthe upper valve ports 192 for the pump chambers 181. In this condition,the pressure in the control chamber for one of the pumps may bemeasured. As is well known in the art, this pressure correlates with the“head” height of the patient, and can be used by the cycler 14 tocontrol the delivery pressure of fluid to the patient. A similarapproach can be used to determine the “head” height of the heater bag 22(which will generally be known), and/or the solution containers 20, asthe head height of these components may have an effect on pressureneeded for pumping fluid in a suitable way.

Noise Reduction Features of the Cycler

In accordance with aspects of the invention, the cycler 14 may includeone or more features to reduce noise generated by the cycler 14 duringoperation and/or when idle. In one aspect of the invention, the cycler14 may include a single pump that generates both pressure and vacuumthat are used to control the various pneumatic systems of the cycler 14.In one embodiment, the pump can simultaneously generate both pressureand vacuum, thereby reducing overall run time, and allowing the pump torun more slowly (and thus more quietly). In another embodiment, the airpump start and/or stop may be ramped, e.g., slowly increases pump speedor power output at starting and/or slowly decreases pump speed or poweroutput at shut down. This arrangement may help reduce “on/off” noiseassociated with start and stop of the air pump so pump noise is lessnoticeable. In another embodiment, the air pump may be operated at alower duty cycle when nearing a target output pressure or volume flowrate so that the air pump can continue operating as opposed to shuttingoff, only to be turned on after a short time. As a result, disruptioncaused by repeated on and off cycles of the air pump may be avoided.

FIG. 126 shows a perspective view of an interior section of the cycler14 with the upper portion of the housing 82 removed. In thisillustrative embodiment, the cycler 14 includes a single air pump 83,which includes the actual pump and motor drive contained within a soundbarrier enclosure. The sound barrier enclosure includes an outer shield,such as a metal or plastic frame, and a sound insulation material withinthe outer shield and at least partially surrounding the motor and pump.This air pump 83 may simultaneously provide air pressure and vacuum,e.g., to a pair of accumulator tanks 84. One of the tanks 84 may storepositive pressure air, while the other stores vacuum. A suitablemanifold and valve arrangement may be coupled to the tanks 84 so as toprovide and control air pressure/vacuum supplied to the components ofthe cycler 14.

In accordance with another aspect of the invention, components thatrequire a relatively constant pressure or vacuum supply during cycleroperation, such as an occluder, may be isolated from the source of airpressure/vacuum at least for relatively long periods of time. Forexample, the occluder 147 in the cycler 14 generally requires a constantair pressure in the occluder bladder 166 so that the patient and drainlines remain open for flow. If the cycler 14 continues to operateproperly without power failure, etc., the bladder 166 may be inflatedonce at the beginning of system operation and remain inflated until shutdown. The inventors have recognized that in some circumstances airpowered devices that are relatively static, such as the bladder 166, may“creak” or otherwise make noise in response to slight variations insupplied air pressure. Such variations may cause the bladder 166 tochange size slightly, which causes associated mechanical parts to moveand potentially make noise. In accordance with an aspect of the bladder166 and other components having similar pneumatic power requirements,may be isolated from the air pump 83 and/or the tanks 84, e.g., by theclosing of a valve, so as to reduce variations of pressure in thebladder or other pneumatic component, thus reducing noise that may begenerated as a result of pressure variations. Another component that maybe isolated from the pneumatic supply is the bladder in the door 141 atthe cassette mounting location 145 which inflates to press the cassette24 against the control surface 148 when the door 141 is closed. Othersuitable components may be isolated as desired.

In accordance with another aspect of the invention, the speed and/orforce at which pneumatic components are actuated may be controlled to asto reduce noise generated by component operation. For example, movementof the valve control regions 1481 to move a corresponding portion of thecassette membrane 15 so as to open or close a valve port on the cassette24 may cause a “popping” noise as the membrane 15 slaps against and/orpull away from the cassette 24. Such noise may be reduced by controllingthe rate of operation of the valve control regions 1481, e.g., byrestricting the flow rate of air used to move the control regions 1481.Air flow may be restricted by, for example, providing a suitably smallsized orifice in the line leading to the associated control chamber, orin other ways.

A controller may also be programmed to apply pulse width modulation(“PWM”) to the activation of one or more pneumatic source valves at amanifold of cycler 14. The pneumatic pressure delivered to variousvalves and pumps of cassette 24 can be controlled by causing theassociated manifold source valves to open and close repeatedly duringthe period of actuation of a valve or pump in cassette 24. The rate ofrise or fall of pressure against membrane 15/control surface 148 canthen be controlled by modulating the duration of the “on” portion of theparticular manifold valve during the actuation period. An additionaladvantage of applying PWM to the manifold source valves is that variablepneumatic pressure can be delivered to the cassette 24 components usingonly a binary (on-off) source valve, rather than a more expensive andpotentially less reliable variable-orifice source valve.

In accordance with another aspect of the invention, the movement of oneor more valve elements may be suitably damped so as to reduce noisegenerated by valve cycling. For example, a fluid (such as a ferro fluid)may be provided with the valve element of high frequency solenoid valvesto damp the movement of the element and/or reduce noise generated bymovement of the valve element between open and closed positions.

In accordance with another embodiment, pneumatic control line vents maybe connected together and/or routed into a common, sound-insulated spaceso that noise associated with air pressure or vacuum release may bereduced. For example, when the occluder bladder 166 is vented to allowthe spring plates 165 (see, for example, FIG. 99) to move toward eachother and occlude one or more lines, the air pressure released may bereleased into a sound insulated enclosure, as opposed to being releasedinto a space where noise associated with the release may be heard moreeasily. In another embodiment, lines that are arranged to release airpressure may be connected together with lines that are arranged torelease an air vacuum. With this connection (which may include a vent toatmosphere, an accumulator or other), noise generated by pressure/vacuumrelease may be further reduced.

Control System

The control system 16 described in connection with FIG. 1 has a numberof functions, such as controlling dialysis therapy and communicatinginformation related to the dialysis therapy. While these functions maybe handled by a single computer or processor, it may be desirable to usedifferent computers for different functions so that the implementationsof those functions are kept physically and conceptually separate. Forexample, it may be desirable to use one computer to control the dialysismachinery and another computer to control the user interface.

FIG. 127 shows a block diagram illustrating an exemplary implementationof control system 16, wherein the control system comprises a computerthat controls the dialysis machinery (an “automation computer” 300) anda separate computer that controls the user interface (a “user interfacecomputer” 302). As will be described, safety-critical system functionsmay be run solely on the automation computer 300, such that the userinterface computer 302 is isolated from executing safety-criticalfunctions.

The automation computer 300 controls the hardware, such as the valves,heaters, and pumps that implement the dialysis therapy. In addition, theautomation computer 300 sequences the therapy and maintains a “model” ofthe user interface, as further described herein. As shown, theautomation computer 300 comprises a computer processing unit(CPU)/memory 304, a flash disk file system 306, a network interface 308,and a hardware interface 310. The hardware interface 310 is coupled tosensors/actuators 312. This coupling allows the automation computer 300to read the sensors and control the hardware actuators of the APD systemto monitor and perform therapy operations. The network interface 308provides an interface to couple the automation computer 300 to the userinterface computer 302.

The user interface computer 302 controls the components that enable dataexchange with the outside world, including the user and external devicesand entities. The user interface computer 302 comprises a computerprocessing unit (CPU)/memory 314, a flash disk file system 316, and anetwork interface 318, each of which may be the same as or similar totheir counterparts on the automation computer 300. The Linux operatingsystem may run on each of the automation computer 300 and the userinterface computer 302. An exemplary processor that may be suitable foruse as the CPU of the automation computer 300 and/or for use as the CPUof the user interface computer 302 is Freescale's Power PC 5200B®.

Via the network interface 318, the user interface computer 302 may beconnected to the automation computer 300. Both the automation computer300 and the user interface computer 302 may be included within the samechassis of the APD system. Alternatively, one or both computers or aportion of said computers (e.g., display 324) may be located outside ofthe chassis. The automation computer 300 and the user interface computer302 may be coupled by a wide area network, a local area network, a busstructure, a wireless connection, and/or some other data transfermedium.

The network interface 318 may also be used to couple the user interfacecomputer 302 to the Internet 320 and/or other networks. Such a networkconnection may be used, for example, to initiate connections to a clinicor clinician, upload therapy data to a remote database server, obtainnew prescriptions from a clinician, upgrade application software, obtainservice support, request supplies, and/or export data for maintenanceuse. According to one example, call center technicians may access alarmlogs and machine configuration information remotely over the Internet320 through the network interface 318. If desired, the user interfacecomputer 302 may be configured such that connections may only beinitiated by the user or otherwise locally by the system, and not byremote initiators.

The user interface computer 302 also comprises a graphics interface 322that is coupled to a user interface, such as the user interface 144described in connection with FIG. 37. According to one exemplaryimplementation, the user interface comprises a display 324 that includesa liquid crystal display (LCD) and is associated with a touch screen.For example, a touch screen may be overlaid on the LCD so that the usercan provide inputs to the user interface computer 302 by touching thedisplay with a finger, stylus or the like. The display may also beassociated with an audio system capable of playing, among other things,audio prompts and recorded speech. The user may adjust the brightness ofthe display 324 based on their environment and preference. Optionally,the APD system may include a light sensor, and the brightness of thedisplay may be adjusted automatically in response to the amount ofambient light detected by the light sensor.

The brightness of the display may be set by the users for two differentconditions: high ambient light and low ambient light. The light sensorwill detect the ambient light level and the control system 16 will setthe display brightness to the preselected levels for either high or lowambient light based on the measured ambient light. The user may selectthe brightness level for high and low ambient light by selection a valuefrom 1 to 5 for each condition. The user interface may be a slider barfor each condition. In another example the user may select a number. Thecontrol system may set the button light levels to match the displaylight levels.

The LCD display and/or the touch screen of the display 324 may developfaults, where they do not display and/or respond correctly. One theory,but not the only theory, of the cause is an electro-static dischargefrom a user to the screen that changes the values in the memories of thedrivers for the LCD display and touch screen. The software processes UICexecutive 354 or the AC executive 354 may include a low prioritysub-process or thread that checks the constant memory registers of thedrivers for the touch screen and LCD display. If thread finds that anyof the constant values in the memory registers are different from thosestored elsewhere in the User Interface computer 302 or automationcomputer 300, then the thread calls for another software process toreinitialize the drivers for LCD display and/or the touch screen. In oneembodiment, the LCD display is driven by a Seiko Epson S1d13513 chip andthe touch screen is driven by Wolfson Microelectronics WM97156 chip.Examples of the constant register values include but are not limited tothe number of pixels display on the screen, the number colors displayed.

In addition, the user interface computer 302 comprises a USB interface326. A data storage device 328, such as a USB flash drive, may beselectively coupled to the user interface computer 302 via the USBinterface 326. The data storage device 328 may comprise a “patient datakey” used to store patient-specific data. Data from dialysis therapiesand/or survey questions (e.g., weight, blood pressure) may be logged tothe patient data key. In this way, patient data may be accessible to theuser interface computer 302 when coupled to the USB interface 326 andportable when removed from the interface. The patient data key may beused for transferring data from one system or cycler to another during acycler swap, transferring new therapy and cycler configuration data fromclinical software to the system, and transferring treatment history anddevice history information from the system to clinical software. Anexemplary patient data key 325 is shown in FIG. 128.

As shown, the patient data key 325 comprises a connector 327 and ahousing 329 coupled to the connector. The patient data key 325 may beoptionally be associated with a dedicated USB port 331. The port 331comprises a recess 333 (e.g., in the chassis of the APD system) and aconnector 335 disposed within the recess. The recess may be defined, atleast in part, by a housing 337 associated with the port 331. Thepatient data key connector 327 and the port connector 335 are adapted tobe selectively electrically and mechanically coupled to each other. Asmay be appreciated from FIG. 128, when the patient data key connector327 and the port connector 335 are coupled, the housing 329 of thepatient data storage device 325 is received at least partially withinthe recess 333.

The housing 329 of the patient data key 325 may include visual cuesindicative of the port with which it is associated and/or be shaped toprevent incorrect insertion. For example, the recess 333 and/or housing337 of the port 331 may have a shape corresponding to the shape of thehousing 329 of the patient data key 325. For example, each may have anon-rectangular or otherwise irregular shape, such as an oblong shapewith an upper indentation as shown in FIG. 128. The recess 333 and/orhousing 337 of the port 331 and the housing 329 of the patient data key325 may include additional visual cues to indicate their association.For example, each may be formed of the same material and/or have thesame or a similar color and/or pattern.

In a further embodiment, as shown in FIG. 129, the housing 329 of thepatient data key 325 may constructed to be sloped away from connector327 to carry any liquids that may splash onto the key 325 away fromconnector 327 and toward the opposite end of the housing 329, where ahole 339 in the housing 329 may help drain the liquid off and away fromthe patient data key 325 and its coupling with the port connector 335.

In one embodiment, the port 331 and recess 333 are located on the frontpanel 1084 of cycler 14 as shown in FIG. 35. The patient data key 325 isinserted in the port 331 before the door 141 is closed and therapy isstarted. The door 141 includes a second recess 2802 to accommodate thepatient data key 325, when the door 141 is closed. Locating the patientdata key 325 behind the door 141 assures that all the therapy data maybe recorded on to the PDK. This location prevents a user from removingthe key mid-therapy.

Alternatively or additionally, the patient data key 325 may comprise averification code that is readable by the APD system to verify that thepatient data key is of an expected type and/or origin. Such averification code may be stored in a memory of the patient data key 325,and be read from the patient data key and processed by a processor ofthe APD system. Alternatively or additionally, such a verification codemay be included on an exterior of the patient data key 325, e.g., as abarcode or numeric code. In this case, the code may be read by a cameraand associated processor, a barcode scanner, or another code readingdevice.

If the patient data key is not inserted when the system is powered on,an alert may be generated requesting that the key be inserted. However,the system may be able to run without the patient data key as long as ithas been previously configured. Thus, a patient who has lost theirpatient data key may receive therapy until a replacement key can beobtained. Data may be stored directly to the patient data key ortransferred to the patient data key after storage on the user interfacecomputer 302. Data may also be transferred from the patient data key tothe user interface computer 302.

In addition, a USB Bluetooth® adapter 330 may be coupled to the userinterface computer 302 via the USB interface 326 to allow, for example,data to be exchanged with nearby Bluetooth®-enabled devices. Forexample, a Bluetooth®-enabled scale in the vicinity of the APD systemmay wirelessly transfer information concerning a patient's weight to thesystem via the USB interface 326 using the USB Bluetooth® adapter 330.Similarly, a Bluetooth®-enabled blood pressure cuff may wirelesslytransfer information concerning a patient's blood pressure to the systemusing the USB Bluetooth® adapter 330. The Bluetooth® adapter may bebuilt-in to the user interface computer 302 or may be external (e.g., aBluetooth® dongle).

The USB interface 326 may comprise several ports, and these ports mayhave different physical locations and be used for different USB device.For example, it may be desirable to make the USB port for the patientdata key accessible from the front of the machine, while another USBport may be provided at and accessible from the back of the machine. AUSB port for the Bluetooth® connection may be included on the outside ofthe chassis, or instead be located internal to the machine or inside thebattery door, for example.

As noted above, functions that could have safety-critical implicationsmay be isolated on the automation computer. Safety-critical informationrelates to operations of the APD system. For example, safety-criticalinformation may comprise a state of a APD procedure and/or thealgorithms for implementing or monitoring therapies. Non safety-criticalinformation may comprise information that relates to the visualpresentation of the screen display that is not material to theoperations of the APD system.

By isolating functions that could have safety-critical implications onthe automation computer 300, the user interface computer 302 may berelieved of handling safety-critical operations. Thus, problems with orchanges to the software that executes on the user interface computer 302will not affect the delivery of therapy to the patient. Consider theexample of graphical libraries (e.g., Trolltech's Qt® toolkit), whichmay be used by the user interface computer 302 to reduce the amount oftime needed to develop the user interface view. Because these librariesare handled by a process and processor separate from those of theautomation computer 300, the automation computer is protected from anypotential flaws in the libraries that might affect the rest of thesystem (including safety-critical functions) were they handled by thesame processor or process.

Of course, while the user interface computer 302 is responsible for thepresentation of the interface to the user, data may also be input by theuser using the user interface computer 302, e.g., via the display 324.To maintain the isolation between the functions of the automationcomputer 300 and the user interface computer 302, data received via thedisplay 324 may be sent to the automation computer for interpretationand returned to the user interface computer for display.

Although FIG. 127 shows two separate computers, separation of thestorage and/or execution of safety-critical functions from the storageand/or execution of non safety-critical functions may be provided byhaving a single computer including separate processors, such asCPU/memory components 304 and 314. Thus, it should be appreciated thatproviding separate processors or “computers” is not necessary. Further,a single processor may alternatively be used to perform the functionsdescribed above. In this case, it may be desirable to functionallyisolate the execution and/or storage of the software components thatcontrol the dialysis machinery from those that control the userinterface, although the invention is not limited in this respect.

Other aspects of the system architecture may also be designed to addresssafety concerns. For example, the automation computer 300 and userinterface computer 302 may include a “safe line” that can be enabled ordisabled by the CPU on each computer. The safe line may be coupled to avoltage supply that generates a voltage (e.g., 12 V) sufficient toenable at least some of the sensors/actuators 312 of the APD system.When both the CPU of the automation computer 300 and the CPU of the userinterface computer 302 send an enable signal to the safe line, thevoltage generated by the voltage supply may be transmitted to thesensors/actuators to activate and disable certain components. Thevoltage may, for example, activate the pneumatic valves and pump,disable the occluder, and activate the heater. When either CPU stopssending the enable signal to the safe line, the voltage pathway may beinterrupted (e.g., by a mechanical relay) to deactivate the pneumaticvalves and pump, enable the occluder, and deactivate the heater. In thisway, when either the automation computer 300 or the user interfacecomputer 302 deems it necessary, the patient may be rapidly isolatedfrom the fluid path, and other activities such as heating and pumpingmay be stopped. Each CPU can disable the safe line at any time, such aswhen a safety-critical error is detected or a software watchdog detectsan error. The system may be configured such that, once disabled, thesafe line may not be re-enabled until both the automation computer 300and user interface computer 302 have completed self-tests.

FIG. 130 shows a block diagram of the software subsystems of the userinterface computer 302 and the automation computer 300. In this example,a “subsystem” is a collection of software, and perhaps hardware,assigned to a specific set of related system functionality. A “process”may be an independent executable which runs in its own virtual addressspace, and which passes data to other processes using inter-processcommunication facilities.

The executive subsystem 332 includes the software and scripts used toinventory, verify, start and monitor the execution of the softwarerunning on the CPU of the automation computer 300 and the CPU of theuser interface computer 302. A custom executive process is run on eachof the foregoing CPUs. Each executive process loads and monitors thesoftware on its own processor and monitors the executive on the otherprocessor.

The user interface (UI) subsystem 334, handles system interactions withthe user and the clinic. The UI subsystem 334 is implemented accordingto a “model-view-controller” design pattern, separating the display ofthe data (“view”) from the data itself (“model”). In particular, systemstate and data modification functions (“model”) and cycler controlfunctions (“controller”) are handled by the UI model and cyclercontroller 336 on the automation computer 300, while the “view” portionof the subsystem is handled by the UI screen view 338 on the UI computer302. Data display and export functionality, such as log viewing orremote access, may be handled entirely by the UI screen view 338. The UIscreen view 338 monitors and controls additional applications, such asthose that provide log viewing and a clinician interface. Theseapplications are spawned in a window controlled by the UI screen view338 so that control can be returned to the UI screen view 338 in thecase of an alert, an alarm or an error.

The therapy subsystem 340 directs and times the delivery of the dialysistreatment. It may also be responsible for verifying a prescription,calculating the number and duration of therapy cycles based upon theprescription, time and available fluids, controlling the therapy cycles,tracking fluid in the supply bags, tracking fluid in the heater bag,tracking the amount of fluid in the patient, tracking the amount ofultra-filtrate removed from patient, and detecting alert or alarmconditions.

The machine control subsystem 342 controls the machinery used toimplement the dialysis therapy, orchestrating the high level pumping andcontrol functionality when called upon by the therapy subsystem 340. Inparticular, the following control functions may be performed by themachine control subsystem 342: air compressor control; heater control;fluid delivery control (pumping); and fluid volume measurement. Themachine control subsystem 342 also signals the reading of sensors by theI/O subsystem 344, described below.

The I/O subsystem 344 on the automation computer 300 controls access tothe sensors and actuators used to control the therapy. In thisimplementation, the I/O subsystem 344 is the only application processwith direct access to the hardware. Thus, the I/O subsystem 344publishes an interface to allow other processes to obtain the state ofthe hardware inputs and set the state of the hardware outputs.

FPGA

In some embodiments, the Hardware Interface 310 in FIG. 132 may be aseparate processor from the automation computer 300 and the UserInterface 302 that may perform a defined set of machine controlfunctions and provide an additional layer of safety to the cyclercontroller 16. A second processor, such as a field programmable gatearray (FPGA) may increase the responsiveness and speed of the cycler 14by moving some computing tasks from the automation computer 300 to thehardware interface 310 (e.g., an FPGA), so that the automation computer300 can devote more resources to fluid management and therapy control,as these comprise resource-intensive calculations. The hardwareinterface 310 may control the pneumatic valves and record andtemporarily store data from the various sensors. The real time controlof the valves, pressure levels and data recording by the hardwareinterface 310 allows the automation computer 300 to send commands andreceive data, when the software processes or functions running on theautomation computer 300 are ready for them.

A hardware interface processor 310 may advantageously be implemented onany medical fluid delivery apparatus, including (but not limited to) aperitoneal dialysis cycler 14, in which fluid is pumped by one or morepumps and an arrangement of one or more valves from one or more sourcecontainers of fluid (e.g., dialysate solution bags, or a heater bagcontaining fluid to be infused) to a patient or user. It may also beimplemented on a fluid delivery apparatus that is configured to pumpfluid from a patient or user (e.g., peritoneal dialysis cycler) to areceptacle (e.g., drain bag). A main processor may be dedicated tocontrolling the proper sequence and timing of pumps and valves toperform specific functions (e.g., pumping from a solution bag to aheater bag, pumping from a heater bag to a user, or pumping from a userto a drain receptacle), and to monitor the volumes of fluid pumped fromone location to the next. A secondary (hardware interface) processor(e.g. an FPGA) may correspondingly be dedicated to collect and storedata received from various sensors (e.g., pressure sensors associatedwith the pumps, or temperature sensors associated with a heating system)at an uninterrupted fixed rate (e.g., about 100 Hz or 2000 Hz), and tostore the data until it is requested by the main processor. It may alsocontrol the pumping pressures of the pumps at a rate or on a schedulethat is independent from any processes occurring in the main processor.In addition to other functions (see below) it may also open or closeindividual valves on command from the main processor.

In one example the Hardware Interface 310 may be a processor thatperforms a number of functions including but not limited to:

-   -   Acquiring pneumatic pressure sensor data on a predictable and        fine resolution time base;    -   Storing the pressure data with a timestamp until requested by        automation computer 300;    -   Validating the messages received from that automation computer        300;    -   Providing automated control of one or more pneumatic valves        2660-2667;    -   Controlling some valves with a variable pulse width modulation        (PWM) duty cycle to provide Pick & Hold functionality and/or        control some valves with current feedback;    -   Provide automated and redundant safety checking of valve        combinations, maximum pressures and temperatures and ability.    -   Independent of the other computers 300, 302 putting the cycler        14 into a failsafe mode as needed.    -   Monitoring status of buttons on the cycler 14 and controlling        the level of button illumination;    -   Controlling the Auto Connect screw-drive mechanism 1321 and        monitoring the Auto-Connect position sensing;    -   Detecting the presence of solution caps 31 and/or spike caps 63;    -   Control of the pneumatic pump;    -   Control of the prime sensor LED and detector;    -   Detecting over-voltages and testing hardware to detect        over-voltages;    -   Controlling and monitoring one or more fluid detectors;    -   Monitoring the latch 1080 and proximity sensor 1076 on the door        141;    -   Monitoring critical voltages at the system level.

The Hardware Interface 310 may comprise a processor separate from theprocessors in the automation computer 300 and user interface 302, A to Dconverters and one or more IO boards. In another embodiment, thehardware interface is comprised of a FPGA (Field Programmable GateArray). In one embodiment the FPGA is a SPARTAN® 3A in the 400K gate and256 ball package made by Xilinx Inc. of California. The HardwareInterface 310 is an intelligent entity that is employed to operate as anindependent safety monitor for many of the Control CPU functions. Thereare several safety critical operations where either the HardwareInterface or the Control CPU serves as a primary controller and theother serves as a monitor.

The hardware interface 310 serves to monitor the following automationcomputer 300 functions including but not limited to:

-   -   Monitoring the integrity of system control data being received        from the automation computer 300;    -   Evaluating the commanded valve configurations for combination        that could create a patient hazard during therapy;    -   Monitoring the fluid and pan temperature for excessive high or        low temperatures;    -   Monitoring and testing the overvoltage monitor; and    -   Provide a means for the automation computer 300 to validate        critical data returned from the hardware interface.

FIG. 131 is a schematic representation of one arrangement of theautomation computer 300, the UI computer 302 and the hardware interfaceprocessor 310. The hardware interface 310 is connected via acommunication line to the automation computer 300 and connects to thesensors and actuators 312 in the cycler 14. A voltage supply 2500provides power for the safety critical actuators that can be enabled ordisabled by any of the computers 300, 302, 310. The safety criticalactuators include but are not limited to the pneumatic valves, thepneumatic pump and a safety relay on the heater circuit. The pneumaticsystem is configured to safe condition when unpowered. The pneumaticsafe condition may include occluding the lines 28,34 to the patient,isolating the control chambers 171 and/or closing all the valves 184,186, 190, 192, on the cassette 24. The safety relay 2030 in the heatercircuit 2212 is open, preventing electrical heating, when the relay isunpowered. Each computer 300, 302, 310 controls a separate electricalswitch 2510 that can each interrupt power to the valves, pump and safetyrelay. If any of the three computers detects a fault condition, it canput the cycler 14 in a failsafe condition by opening one of the threeswitches 2510. The electrical switches 2510 are controlled by the safetyexecutive process 352, 354 in the UI computer 302, and automationcomputer 300 respectively.

FIG. 132 is a schematic illustration of the connections between theHardware Interface 310, the various sensors, the pneumatic valves, thebag heater and the automation computer 300. The Hardware Interface 300controls each of the pneumatic valves 2660-2667 and the pneumatic pumpor compressor 2600 via pulse-width-modulated DC voltages. FIG. 132presents an alternative embodiment of the safe line 2632 supplying powerto the pneumatic valves 2660-2667, pump 2600 and heater safety relay2030, in which a single switch 2510 is driven by an AND gate 2532connected to the three computers 300, 302, 310. The prime sensor iscontrolled and monitored by the Hardware Interface 310. The brightnessof the button LEDs is controlled by the Hardware Interface 310 via aPWM'd voltage.

The data signals from the buttons, pressure sensors, temperature sensorsand other elements listed in FIG. 132 are monitored by the HardwareInterface 310, and the data is stored in a buffer memory until calledfor by the automation computer 300. The digital inputs are connecteddirectly to the Hardware Interface 310. The analog signals frompressure, temperature, current sensors and others are connected toAnalog-to-Digital-Converter (ADC) boards that convert the analog signalsto digital values and may a scale and/or offset the digital values. Theoutputs of the ADCs are communicated over SPI buses to the HardwareInterface 310. The data is recorded and stored in the buffer at a fixedrate. Some of the data signals may be recorded at a relatively slowrate, including the pressure data on the pressure reservoirs and thefluid trap, temperatures, and current measurements. The low speed datamay be recorded at 100 Hz. The adiabatic FMS volume measurementalgorithm can be improved with high speed pressure data that is recordedat regular intervals. In a preferred embodiment, the pressure data fromthe sensors on the control volume 171 and the reference chamber 174 arerecorded at 2000 Hz. The data may be stored in random-access-memory(RAM) along with a time stamp. The rate of data collection maypreferably proceed independently of the automation computer 300 and ofprocesses or subroutines on the hardware interface. The data is reportedto the automation computer 300, when a process calls for that value.

The transfer of data between the hardware interface 310 to theautomation computer 300 may occur in a two step process where a datapacket transferred and stored in a buffer before being validated andthen accepted for use by the receiving computer. In one example, thesending computer transmits a first data packet, followed by a secondtransmission of the cyclic redundancy check (CRC) value for the firstdata packet. The receiving computer stores the first data packet in amemory buffer and calculates a new CRC value first data packet. Thereceiving computer then compares the newly calculated CRC value to theCRC value received and accepts the first data packet if the two CRCvalues match. The cyclic redundancy check (CRC) is an error-detectingcode commonly used in digital networks and storage devices to detectaccidental changes to raw data. Blocks of data entering these systemsget a short check value attached, based on the remainder of a polynomialdivision of their contents; on retrieval the calculation is repeated,and corrective action can be taken against presumed data corruption ifthe check values do not match. The data is not transferred between theautomation computer and hardware interface if CRC values do not match.If multiple consecutive data packets fail the CRC test, the receivingcomputer may signal an alarm and put the machine in a fail-safecondition by de-energizing the safe line 2632. In one example, the alarmcondition occurs on the third consecutive failed CRC check.

The automation computer 300 passes commands to open selected valves andset specified pressures in specified volumes to the hardware interface300. The hardware interface 310 in turn controls the valve position byproviding a PWM'd voltage to each valve. The hardware interface 310opens valves as requested with a pick-and-hold algorithm, where thevalve is initially actuated with a high voltage or current, and thenheld in place with a lower voltage or current. Pick-and-hold operationof valves may advantageously reduce the power draw and the level of heatdissipation inside the cycler 14.

The hardware interface 310 controls the pressure in the specified volumeby opening and closing the valves between the specified volume and theappropriate pressure reservoir based on the measured pressure in thespecified volume. The hardware interface 310 may also control thepressure in the pressure reservoirs by opening and closing the valvesbetween a pneumatic pump and one of the pressure reservoirs based on themeasured pressure in the reservoir. The specified volumes may includeeach of the control chambers 171, the reference volumes 174, the fluidtrap and the positive and negative reservoirs. The hardware interface310 may control the pressure in each of these specified volumes via anumber of control schemes, including but not limited to on-off control,or proportional control of the valve with a PWM signal. In one example,as described above, the hardware interface 310 implements an on-offcontroller, sometimes referred to as a bang-bang controller, which setsa first and second limit and closes the valve when the pressure exceedsthe upper second limit and opens the valve when the pressure is lessthan the first lower limit. In another example, the hardware interface310 may operate valves between the specified volume and both pressurereservoirs to achieve a desired pressure. In other examples theautomation computer 300 may specify one or more valves and command aspecific valve to control the pressure as measured by a specifiedsensor.

The hardware interface 310 controls the position and operation of theAuto-Connect carriage. The movement and positioning of the Auto-Connectcarriage 146 is controlled in real time by the hardware interface basedon the measured position of the carriage 146. The automation computer300 may command a particular function or position for the carriage. Thehardware interface 310 carries out the commanded function withoutburdening memory or processing of the automation computer 300. Thepositioning of the carriage 146 is controlled with a feedback loop froma position sensor. In addition, the FPGA detects the presence ofsolution caps 31 and/or spike caps 63 with sensing elements 1112 asdescribed above. Alternatively, the presence of the caps 31 and/or spikecaps 63 can be detected by a range of sensing technologies, includingbut not limited to vision systems, optical sensors that can be blockedby a solution cap 31 and/or spike cap 63, or, for example, amicro-switch on the stripper element 1491.

The hardware interface 310 may implement safety functions independentlyof the automation computer 300 or the user interface computer 302. Theindependent action of the hardware interface 310 to disable the safetyline 2632 and/or signal an alarm to the safety executives 352, 354further reduces the possibility of an unsafe condition occurring. Thehardware interface 310 may send an alarm and/or de-energize the safeline 2632 for defined valve combinations at any time. Shutting thecycler down based on disallowed valve positions protects the patient andpreserves the ability to complete the therapy (after a reset if needed).The hardware interface 310 may also alarm and de-energize the safe lineat unsafe conditions including excessive temperature on the heater panand/or bag button, excessive pressure in control chamber or reservoir.The hardware interface may alarm and de-energize the safe line whenwater or other liquid is detected in the fluid trap.

Heater Control System

The following descriptions of a heater control system, including (butnot limited to) a dual-voltage heater control system and a heatercurrent leakage optimization and safety system may be applied to anydevice that operates a heater at high (e.g., line) voltages. Forexample, these heater control systems may be incorporated into thepresently disclosed peritoneal dialysis cycler. In addition, they may beincorporated into peritoneal dialysis systems disclosed in U.S. Pat.Nos. 5,350,357, 5,431,626, 5,438,510, 5,474,683 and 5,628,908, or anyhemodialysis system, such as a hemodialysis system disclosed in U.S.Pat. Nos. 8,246,826, 8,357,298, 8,409,441 and 8,393,690.

The control systems described above may be used to ensure that thesolution delivered to a patient is maintained within a pre-determinedrange of temperatures. During the therapy process, the cycler 14 fillsthe heater bag 22 with solution from the connected solution containers20, via a heater bag line 26. The heater bag 22 rests on the heater pan142 which may include electrical resistance heaters. The heater bag 22may be covered with an insulated cover 143. A heater controller mayfunction so as to control the thermal energy delivered to the heater pan142 in order to control the temperature of the solution to a desired setpoint prior to delivering the solution to the patient. The solutiontemperature should be within a safe range prior to being delivered tothe patient's abdominal cavity in order to avoid injuring or causingdiscomfort to the patient, or causing hypothermia or hyperthermia. Theheater controller may also limit the temperature of the heater pan totouch-safe temperatures. The heater controller is constructed to heatand maintain the solution within a range of acceptable temperatures in atimely manner in order to ensure the most effective therapy.

FIG. 133 is a schematic view of an exemplary embodiment of a solutionheater system 500. In this example, the solution heater system 500 islocated within the housing 82 of the cycler 14. The housing includes aninsulated lid 143 that may be affixed to the top of the housing 82. Thehousing 82 and the heater lid 143 may therefore define a region thatserves to house the components of the solution heater system 500. Thesolution heater system may include the following elements: housing 82,heater lid 143, heater pan 22, heater elements 508, heater pantemperature sensors 504, button temperature sensor 506, insulating ring507 and heater control electronics 50. The heater pan 142 is positionedinside the housing 82, and may accommodate a heater bag 22 whenpositioned on top of the heater tray 142. Preferably, the heater pan 142is inclined to place the inlet and/or outlet of the heater bag in adependent position, to help ensure that fluid in the bag is always incontact with the inlet/outlet regardless of the amount of fluid in thebag. In an embodiment, there can be up to six or more heater pantemperature sensors 504 (only one exemplary heater pan temperaturesensor 504 is shown in FIG. 133) positioned along the floor of theheater pan 142. Additionally, there may be a button temperature sensor506 positioned within the heater pan 142. The button sensor 506 ispositioned to make good thermal contact with the heater bag, while beingthermally isolated from the heater pan 142 by an insulating ring 507, inorder to provide an approximation of the temperature of the fluid ordialysate in the bag. In another embodiment, the button sensor 506 maycomprise a pair of thermistors mounted on an aluminum button. Thealuminum button is thermally isolated by an insulating ring made of, forexample, LEXAN® 3412R plastic or another low thermal conductivitymaterial. The button temperature sensor 506 may be located near the endof the tray where the fluid lines connect to the heater bag 22 in orderto better measure the temperature of the fluid within the heater bagwhen the heater bag is less than approximately one-third full. Thebutton sensor 506 may also be referred to as the fluid or dialysatetemperature sensor. There may also be a plurality of heater elements 508positioned under the heater pan 142, more toward the superior end of thepan, with the bag sensor located more toward the dependent portion ofthe pan, in order for the sensor to provide a more accurate reading ofthe fluid temperature within the bag, and to be relatively unaffected bythe heater elements 508. The thermal output of the heater elements 508may be controlled by the heater control electronics 505 to achieve thedesired fluid temperature in the heater bag. The heater controlelectronics 505 may include but not be limited to a heater controlmodule 509 that produces a Pulse Width Modulation (PWM) signal (PWMsignal 511, represented in FIG. 134). Electrical hardware in theinput-output (IO) subsystem 344 connects electrical power to the heaterelements 508 based on the PWM signal 511, and hardware on the IOsubsystem 344 reads the output of heater pan temperature sensors 504 andbutton temperature sensor 506. The PWM signal 511 may control the powersupplied to each of the heater elements 508, and consequently thesolution heater system 500 may then heat the heater bag 22 to auser-settable comfort temperature, which may be controlled within apreferred safe temperature range. The solution heater system 500 mayalso limit the surface temperature of the heater pan 142 to asafe-to-touch temperature. The hardware components of the heater controlcircuitry 505 may be part of controller 16. There may also be insulation510 positioned below the heater element 508 which functions to thermallyisolate the heater pan 142 and heater bag 22 from the electronic andpneumatic components of the cycler 12. Additionally, the heater lid 143may insulate the heater bag 22 from the surrounding environment. Thesolution heater system 500 may thus be constructed to bring the solutiontemperature inside the heater bag 22, as measured by the buttontemperature sensor 506, to the desired fluid set point temperature 550(see FIG. 135) as quickly as possible, and maintaining that desiredfluid set point temperature 550 through the rest of the therapy cycle.In some embodiments, the temperature sensors connect to the hardwareinterface 310. The same hardware interface 310 may control a safetyrelay that disables the heater.

In some embodiments, the heater elements may include thermal switchesthat open when the temperature of the switch exceeds a firstpre-determined value. The switch will close again once the temperatureof the switch drops below the second lower pre-determined value. Thethermal switch may be incorporated directly into the heater elements ormay be mounted on the outside of the heater element or on the heaterpan. The thermal switches provide an additional layer of protectionagainst unsafe pan temperatures.

In another example, the thermal switch may be a thermal fuse with aone-time fusible link. A service call will be required to replace theblown thermal fuse, which may advantageously provide an opportunity toinspect and/or test cycler 14 before restarting therapy. FIG. 134 showsa schematic block diagram of the software context of the heater controlsubsystem. In an embodiment, the logic of the heater control circuitry505 may be implemented as a heater control module 509 in the machinecontrol subsystem 342 in the APD System software architecture. Theheater controller software may be implemented in the controller 16 (FIG.127) as described below. Additionally, the therapy subsystem 340 maysupply information to the machine control subsystem 342 such as theheater bag volume and the set point for the button temperature sensor506. The heater elements 508 may be enabled by the therapy subsystem340. The machine control subsystem 342 may also read temperature valuesfrom the I/O subsystem 344, which is located below the machine controlsubsystem 342. Furthermore, the heater controller 509 may output a PWMsignal 511 which may then control the power supplied to the heaterelements 508.

In an embodiment, the machine control subsystem 342 may be calledperiodically (e.g., approximately every 10 milliseconds) to service theI/O subsystem 344, update variables, and detect conditions. The machinecontrol subsystem 342 may also send updated signals to the heatercontrol module 509 periodically (e.g., approximately every 10 ms.). Theupdated signals may include the heater bag volume, heater pantemperatures 515, the button temperature 517, the set point temperature550 and the heater enable function. The heater control module mayaverage some or all of these signals continuously, but only calculateand update its output 511 at a lower frequency (e.g., every 2 seconds).

In another aspect, the solution heater system 500 may be able to controlthe solution temperature in the heater bag 22 within a given range of adesired fluid set point temperature 550 (see FIG. 134 and FIG. 139-141).Furthermore, the solution heater system 500 has been designed tofunction within pre-defined specifications under a variety of differentoperating conditions, such as a relatively wide range of ambienttemperatures (e.g., approximately 5° C. to approximately 37° C.), bagfill volumes (e.g., approximately 0 mL to approximately 3200 mL), andsolution container 20 temperatures (e.g., between approximately 5° C.and approximately 37° C.). In addition, the solution heater system 500is capable of functioning within specifications even if the solution inthe heater bag 22 and the solution introduced during the replenish cyclemay be at different temperatures. The solution heater system 500 hasalso been designed to function within specifications with heater supplyvoltages varying as much as +10% of nominal voltage.

The solution heater system 500 may be considered to be an asymmetricalsystem, in which the solution heater system 500 can increase thesolution temperature with the heater elements 508, but relies on naturalconvection to lower the solution temperature in the heater bag 22. Theheat loss may be further limited by the insulation 510 and the insulatedcover 143. One possible consequence is that in the event of atemperature overshoot, the APD system 10 may delay a patient fill whilethe heater bag slowly cools. A possible consequence of placing theheater elements on the heater pan 142 is that the heater pan 142 may beat a substantially higher temperature than that of the heater bag 22during the heating process. A simple feedback control on the heater bagtemperature as recorded by the button temperature sensor 506, may notturn the heater off soon enough to avoid the thermal energy at a highertemperature in the heater pan from causing the heater bag 22 toovershoot the desired set point temperature 550. Alternativelycontrolling the heaters 508 to achieve a heater pan temperature 504 thatwould not cause the heater bag temperature to overshoot may result in aslow heater system and thus delay therapy.

In order to minimize the time for the solution in the heater bag toachieve the set point temperature 550 without overshoot, the heatercontrol module may implement a control loop that varies the electricalpower of the heater elements 508 to achieve a desired fluid temperaturein the heater bag, in part by controlling the equilibrium temperature ofthe heater pan 142, the heater bag 22 and the fluid within the heaterbag 22. In one embodiment, a Proportional-Integral (PI) controllercontrols an equilibrium temperature 532 that is a function of thetemperatures of the heater bag 22 and the heater pan 142 and the volumeof solution in the heater bag. The equilibrium temperature may beunderstood to be the temperature that the solution in the heater bag 22and the heater pan 142 would reach if the heater were turned off and thetwo components allowed to reach equilibrium. The equilibrium temperaturemay also be understood as the weighted average of the target temperaturefor the heater pan 142 and the measured temperature of thesolution-filled heater bag, weighted by the thermal capacitance of each.The equilibrium temperature may also be calculated as the weightedaverage of the measured heater pan temperature and the solutiontemperature, in which the temperatures are weighted by their respectivethermal capacitances. In an embodiment, the weighted average temperatureof the heater pan and fluid in the heater bag may be calculated as thesum of the target heater pan temperature times the thermal capacitanceof the heater pan plus the fluid temperature times the thermalcapacitance of the fluid in the heater bag, where the sum is divided bythe sum of the thermal capacitance of the heater pan plus the thermalcapacitance of the fluid in the heater bag. The weighted averages of theheater pan and fluid may be alternatively weighted by the mass of theheater pan and fluid in the bag or the volume of the heater pan andfluid in the bag.

The control of the equilibrium temperature may be implemented using anumber of control schemes, such as, for example, single feedback loopsusing proportional, integral and or derivative controllers and nestedloops. One embodiment of a control scheme using cascaded nested controlloops is shown in FIG. 135. The outer loop controller 514 may controlthe heater bag temperature as measured by the button temperature sensor506 to the fluid set point temperature 550 by varying the heater pan setpoint temperature 527 supplied to the inner loop controller 512.Alternatively, the outer loop controller 514 may control the equilibriumtemperature of the heater bag 22, fluid and heater pan 142 to the fluidset point temperature 550 by varying the heater pan set pointtemperature 527. The temperature of the heater bag 22 and fluid may bemeasured by the button temperature sensor 506 and the heater pantemperature may be measured by one or more of the heater pan temperaturesensors 504. The outer loop controller may include one or more of thefollowing elements: proportional controller, integral controller,derivative controller, saturation limits, anti-windup logic andzero-order hold logic elements.

The inner loop controller 512 may control the heater pan temperature tothe heater pan set point temperature 527 by varying the thermal outputof the heater elements 508. The temperature of the pan may be measuredby one or more of the heater pan temperature sensors 504. The inner loopcontroller may include one or more of the following elements:proportional controller, integral controller, derivative controller,saturation limits, anti-windup logic and zero-order hold logic elements.

An exemplary implementation of the heater control module 509 utilizes aPI regulator cascade-coupled with a Proportional-Integral-Derivative(PID) controller. In the FIG. 135 embodiment, a PID inner loopcontroller 512 may control the temperature of the heater pan 142, and aPI outer loop controller 514 may control the equilibrium temperature ofthe heater bag, the fluid in the heater bag and the heater pan asmeasured by the heater pan temperature sensors 504 and buttontemperature sensor 506. The loop controller 514 differs from a standardPI regulator in that any overshoot of the desired fluid set point 550 bythe solution heater system 500 may be minimized by a logic controllableintegrator as described below. In an embodiment, the heater pantemperature signal 515 and the button temperature sensor (heater bag)signal 517 are low-pass filtered through a pair of control filters 519at a relatively high frame rate (e.g., a full 100 Hz frame rate), whilethe heater control module 509 may change the output of the heaters at alower rate (e.g., rate of ½ Hz).

FIG. 136 shows a schematic diagram of one embodiment of the inner loopcontroller 512 (heater pan controller). In this embodiment, the innerloop controller 512 uses a standard PID regulator including but notlimited to a differencing element 519 to produce a temperature error anda proportional gain element 522 to create an PWM signal 511. The innerloop controller 512 may further include a discrete-time integrator 516to reduce the offset error. The inner loop controller 512 may alsoinclude an anti-windup logic element 518 to minimize overshoot due atemperature error existing for a long period of time when the output ofthe inner loop controller 512 is saturated. The inner loop controller512 may further include a discrete derivative term 520 that acts on theheater pan actual temperature 515 to improve heater responsiveness. Theinner loop controller 512 may further include a saturation limit element521 that sets a maximum and/or minimum allowed heater command or PWMsignal 511. The inner loop controller 512 may further include zero-orderhold logic 523 to hold the PWM signal 511 constant between controllercalculations that occur approximately every 2 seconds.

FIG. 137 shows a schematic diagram of the outer loop controller 514(button temperature sensor controller). In this example, the outer loopcontroller 514 utilizes a modified PI-type regulator, which may includedifferencing elements 531, an integrator 534 and a proportional gainelement 526. The outer loop controller 514 may further include anintegrator switching logic 522 and corresponding switch 529, to allowthe integrator to be switched on or off by logic in the heater controlmodule 509. The outer loop controller 514 may further include a commandfeed forward 524 to improve the responsiveness of the outer loopcontroller 514. The outer loop controller 514 may further include aproportional feedback term 526 to act on a weighted combination of thebutton temperature sensor target temperature 517 and the heater pantarget temperature 527. The resulting measurement is an equilibriumtemperature 532 as described above. The outer loop controller 514 mayfurther include a saturation limit element 521 and/or a low pass filter542. The saturation limit element 521 in the outer loop sets a maximumallowed target pan temperature 527. The low pass filter 542 may bedesigned to filter out transient control signals at frequencies outsidethe bandwidth of the solution heater system 500.

The integral elements 534 in the outer loop controller 514 may be turnedon by a switch 529 when some or all of the following conditions arepresent: the rate of change of the button temperature 517 is below apre-determined threshold, the button temperature 517 is within apre-determined number of degrees of the fluid set point temperature 550,or the bag volume is greater than a pre-determined minimum and neitherof the controllers 512, 514 are saturated. An equilibrium temperaturefeedback loop may control the transient behavior of the solution heatersystem 500, and may be dominant when the surrounding ambient temperatureis in a normal to elevated range. The action of the integrator 516 mayonly be significant in colder environments, which may result in asubstantial temperature difference between the button sensor actualtemperature 517 and the heater pan actual temperature 515 atequilibrium. The feed-forward term 524 may pass the fluid set pointtemperature 550 through to the heater pan target temperature 527. Thisaction will start the heater pan target temperature 527 at the fluid setpoint temperature 550, instead of zero, which thereby improves thetransient response of the solution heater system 500.

The heater module 509 may also include a check that turns off the PWMsignal 511 if the heater pan actual temperature 515 crosses apre-determined threshold (this threshold may be set to be slightlyhigher than the maximum allowed heater pan target temperature 527). Thischeck may not be triggered under normal operation, but may be triggeredif the heater bag 22 is removed while the temperature of the heater pan142 is at a pre-determined maximum value.

The PI controller 514 may include a proportional term that acts on theequilibrium temperature 532. The equilibrium temperature is the heaterbag temperature measured by the button sensor 506 that would result ifthe heater 508 was turned off and the heater pan 142 and thesolution-filled heater bag 22 were allowed to come to equilibrium. Theequilibrium temperature can be better understood by referring to FIG.138, which shows a schematic block diagram of the heater pan 142 andheater bag 22 in a control volume analysis 546. The control volumeanalysis 546 depicts a model environment in which the equilibriumtemperature 532 may be determined. In this illustrative embodiment, thesolution heater system 500 may be modeled in as control volume 548,which may comprise at least two thermal masses: the heater pan 142 andthe heater bag 22. The boundary of the control volume 548 may be assumedto function as a perfect insulator, in which the only heat transfer isbetween the heater pan 142 and the heater bag 22. In this model, thermalenergy 549 may be added to the system via the heater elements 508, butthermal energy may not be removed from the heater pan 142 and heater bag22. In this model, as in the solution heater system 500, it is desirableto heat the heater pan 142 just enough that the heater bag 22 reachesits target temperature as the heater pan 142 and heater bag 22 come toequilibrium. Therefore, the equilibrium temperature 532 may becalculated as a function of the initial temperature of the heater bag 22and the initial temperature of the heater pan 142:E=M _(p) c _(p) T _(p) +V _(b)ρ_(b) c _(b) T _(b)=(M _(p) c _(p) +V_(b)ρ_(b) c _(b))T _(e)where M_(P), c_(p) are the mass and specific heat of the heater pan 142,V_(P), ρ_(b), c_(b) are the volume, density and specific heat of thesolution in the bag, T_(p) and T_(b) are the temperatures of the heaterpan 515 and the button 517 respectively. Solving for the equilibriumtemperature yields a linear combination of pan and button temperatures:

T_(e) = cT_(b) + (1 − c)T_(p) where$C = {{\frac{V_{b}}{k + V_{b}}\mspace{14mu}{and}\mspace{14mu} k} = \frac{M_{p}C_{p}}{\rho_{b}C_{b}}}$

The constant c is an equilibrium constant, k is the thermal capacitanceratio of the heater pan over the solution. The subscript b denotes thesolution in the heater bag 22, while p denotes the heater pan 142.

In this model, allowing the heater module 509 to control the equilibriumtemperature 532 during the initial transient may allow for rapid heatingof the heater bag 22 while also reducing the heater pan actualtemperature 515 sufficiently early to prevent thermal overshoot. The cparameter may be determined empirically. The heater module 509 may set cto a value larger than the measured value to underestimate the totalenergy required to reach the desired set point 550, further limiting thethermal overshoot of the solution heater system 500.

FIG. 139 shows graphically the performance of solution heater system 500of the disclosed embodiment operating under normal conditions. Themeasured temperatures of the heater pan sensors 504, the buttontemperature sensor 506 and an additional temperature probe are plottedagainst time. The fluid temperature probe was part of the experimentalsetup up to verify the control scheme. The fluid probe temperature isshown as line 552. The button temperature is shown as line 517 and theheat pan temperatures are shown as line 515. Line 550 is the targettemperature for the button temperature sensor 506. At the start of thistrial, the heater bag is substantially empty, the heater is off andfluid is not moving, so that all the temperatures are at a nominalvalue. At a time T=1, the fluid at 25 C starts to flow into the heaterbag 22 bringing down the probe and button temperatures 552, 517, whilethe heater turns on and increases the heater pan temperature 515. Undernormal operation, proportional control of the equilibrium temperature532 may be sufficient to heat the solution within the heater bag 22 to atemperature close to the desired fluid set point temperature 550.Therefore, in FIG. 139, the solution heater system 500 functionseffectively, and the heater pan actual temperature 515, the buttonsensor actual temperature 517, and a probe temperature 552 all convergeto the fluid set point temperature 550 within approximately 50 minutes.

FIG. 140 shows graphically the performance of the solution heater system500 operated in a high temperature environment in which the ambienttemperature is 35 C. As described above, the trial begins with theheater bag being substantially empty. Once the fluid starts to flow andthe heater turns on, the probe and button temperatures 552, 517 decreaseand the heater pan temperature 515 increases. In a high temperatureenvironment, the solution heater system 500 functions in a mannersubstantially similar to normal conditions. Thus, proportional controlof the equilibrium temperature 532 may again be sufficient to heat thesolution within the heater bag 22 to a temperature close to the desiredfluid set point temperature 550. In FIG. 139, the solution heater system500 functions effectively and within desired specifications, and theheater pan actual temperature 515, the button sensor actual temperature517, and a probe temperature 552 all converge to the desired set pointtemperature 550 within approximately 30 minutes.

FIG. 141 shows graphically the performance of the solution heater system500 operated in a cold environment where the ambient temperature is 10degrees C. and the source fluid is 5 degrees C. As described above, thetrial begins with the heater bag being substantially empty. Once thefluid starts to flow and the heater turns on, the probe and buttontemperatures 552, 517 decrease and the heater pan temperature 515increases. In a cold environment, setting the desired fluid set pointtemperature 550 equal to the equilibrium temperature 532 may lead to asteady-state error in the temperature of the button sensor 506. The heatloss in cold environments may necessitate a large temperature differencebetween the heater pan 142 and the button sensor 506 during thermalequilibrium. Since the equilibrium temperature 532 is a weighted sum ofthe heater pan 142 and the button sensor 506, the temperature of thebutton sensor 506 may be below the fluid set point temperature 550 ifthe temperature of the heater pan 142 is above the desired fluid setpoint temperature 550 at equilibrium. This may occur even if theequilibrium temperature 532 is equal to the fluid set point temperature550. To compensate for this steady-state-error an integral term may beadded to outer PI controller 514 that acts on the temperature error ofthe button sensor 506. The integrator 538 may be turned on when one ormore of the following conditions are met: a first derivative of thetemperature of the button sensor 506 is low; the button sensor 506 isclose to the fluid set point temperature 550, the volume of the heaterbag 22 exceeds a minimum threshold; and neither inner PID loop 512 orouter PI controller 514 are saturated. In this illustrative embodiment,the switching of the integral term may minimize the effect of theintegrator 538 during normal operation and may also minimize theovershoot caused by integration during temperature transients.Therefore, in FIG. 141, the solution heater system 500 functionseffectively and within desired specifications, and the heater pan actualtemperature 515, the button sensor actual temperature 517, and a probetemperature 552 all converge to the fluid set point temperature 550within approximately 30 minutes.

In summary, the disclosed temperature controller can achieve goodthermal control of a two component system, in which the mass of thefirst component varies over time, and in which the second componentincludes a heater or cooler, and both components are in an insulatedvolume. This thermal control can be achieved by controlling theequilibrium temperature. The temperature controller determines thetemperature of both components as well as the mass of the variablecomponent. The temperature controller varies the heating or cooling ofthe second component to bring the equilibrium temperature to the desiredset point temperature. The equilibrium temperature is the thermalcapacitance weighted average temperature of the two components. Thecontroller may use a proportional feedback loop to control theequilibrium temperature.

The temperature controller may also include an integral term thatresponds to the difference between the set point temperature and thetemperature of the first component. The integral term optionally may beturned on when some or all of the following conditions are met:

-   the rate of temperature change of the first component is low;-   the temperature of the first part is near the set point temperature;-   the volume of the first part exceeds some minimum level;-   the control output signal is not saturated.

The temperature controller may also include a feed-forward term thatadds the set point temperature to the output of the proportional andintegral terms.

Further, the temperature controller may be the outer loop controller ofa cascade temperature controller in which the outer loop controllerincludes at least a proportional control term on the equilibriumtemperature and outputs a set point temperature for the innercontroller. The inner controller controls the temperature of the firstcomponent with the heater or cooler elements to the set pointtemperature produced by the outer controller.

Universal Power Supply

In accordance with an aspect of the disclosure, the APD system 10 mayinclude a universal power supply that converts line voltage to one ormore levels of DC voltage for some or all of the electro-mechanicalelements and electronics in the cycler 14, and provides AC power to theelectric heater for the heater pan 142. The electro-mechanical elementsin the cycler 14 may include pneumatic valves, electric motors, andpneumatic pumps. The electronics in the cycler 14 may include thecontrol system 16, display 324, and sensors. AC power is supplied to aheater controller to control the temperature of the solution in theheater bag 22 on the heater tray 142 to a desired set point prior todelivering the solution to the user/patient. The universal power supplychanges the configuration of two (or more) heater elements toaccommodate two ranges of AC line voltages: e.g., a first range of110±10 volts rms; and a second range of 220±20 volts rms. Thisarrangement is intended to accommodate using the APD system 10 in anumber of different countries. During the start of a therapy session,the APD cycler 14 fills the heater bag 22 with solution from theconnected solution containers 20, via a heater bag line 26. In analternative embodiment, a pre-filled bag of solution may be placed on aheater pan 142 at the start of a therapy.

PWM Heater Circuit

The heater controller in the APD cycler modulates the electrical powerdelivered to the heater elements attached to the heater pan 142. The APDcycler may be used in various locations around the world and may beplugged into AC mains that supply power from 100 to 230 volts rms. Theheater controller and circuits may adapt to the variety of AC voltageswhile continuing to supply sufficient heater power and not blowing fusesor damaging heater elements in a number of ways.

One embodiment of a heater circuit is presented in FIG. 142, where apulse width modulator (PWM) based circuit 2005 controls the temperatureof the heater pan 142 with a pulse-width-modulated (PWM) element 2010connected between one lead of the AC mains 2040 and the heater element2000. The controller 2035 is operably connected to the relay 2030 andthe PWM element 2010. The controller 2035 monitors the operation of theheater by interrogating the voltage detect 2020 and temperature sensor2007. The controller 2035 may modulate the amount of power delivered tothe heater 2000 via a signal to the PWM element 2010. The PWM orpulse-width-modulated element is closed for some fraction of a fixedperiod between 0 and 100%. When the PWM element 2010 is closed 0% of thetime, no electrical energy flows to the heater 2000. The heater iscontinuously connected to the AC mains 2040 when the PWM element isclosed 100%. The controller 2035 can modulate the amount of powerdissipated by the heater 2000 by setting the PWM element 2010 to a rangeof values between 0 and 100%, inclusive.

The PWM elements 2010 switch large current flows on and off multipletimes a second. PWM elements 2010 are typically some kind of solid staterelay (SSR). SSRs for AC voltage typically include a triggering circuitthat controls the power switch. The triggering circuit may be, forexample, a reed relay, a transformer or an optical coupler. The powerswitch may be a silicon controlled rectifier (SCR) or a TRIAC. The SCRor TRIAC are also referred to as thyristors. One example of a SSR is theMCX240D5® by Crydom Inc.

In one example, the controller 2035 may modulate the PWM element valuein order to control the temperature of the heater pan 142 as measured bytemperature sensor 2007. In another example, the controller 2035 maymodulate the PWM element value to control the temperature of the fluidin the heater bag 22. In another example the controller 2935 may controlthe PWM element 2010 to provide a fixed schedule of heater power. Thecontroller 2035 may command a safety relay 2030 that opens the heatercircuit and stops the flow of electrical power to the heater 2000. Thesafety relay 2030 may be controlled by a separate controller (not shown)in order to provide a safety circuit independent of the controller 2035.

The PWM based circuit 2005 may include a voltage detect element 2020that provides a signal to the controller 2035 indicative of the voltageon the AC mains 2040. In one example, the voltage detect element 2020may measure the AC potential across the AC mains 2040. In anotherexample the voltage detect element 2020 may measure the current flowthrough the heater 2000. The controller 2035 may calculate the voltageacross the AC mains from a known resistance of the heater element 2000,the PWM element 2010 signal and the measured current.

The PWM based circuit 2005 may vary the maximum allowed duty cycle ofPWM element 2010 to accommodate different AC Mains voltage. The heaterelement 2000 may be designed to provide the maximum required power withthe lowest possible AC voltage. The controller may vary the duty cycleof the PWM element 2010 to provide a constant maximum heater power for arange of voltages at the AC mains. For example, the voltage supplied tothe heater 2000 from a 110 volt AC line may be supplied at a 100% dutycycle, and the same amount of electrical power may be delivered to theheater 2000 from a 220 volt AC line if the PWM element 2010 is set to25%. The duty cycle of the PWM element 2010 may be further reduced belowthe maximum value to control the temperature of the heater pan 142.

The temperature of the heater element 2000 and the heater pan 142 may becontrolled by the average heater power over a time constant that is afunction of the thermal mass of the element and heater pan. The averageheater power may be calculated from the heater resistance, which isrelatively constant, and the rms voltage across the heater element 2000.In a practical sized heater, the PWM frequency is much faster than thetime constant of the heater system, so the effective voltage across theheater element is simply the PWM duty cycle multiplied by the rmsvoltage.

One method to control the heater pan temperature of the circuit in FIG.142 may direct the controller 2035 to set a maximum PWM duty cycle basedon the measured voltage at 2020. The maximum duty cycle may becalculated from the desired maximum heater power, known resistance ofthe heater element 2000 and the measured voltage. One possible exampleof the calculation is:PWM _(MAX)=(P _(MAX) *R _(HEATER))^(0.5) /V _(rms)where PWM_(MAX) is the maximum allowed PWM duty cycle, P_(MAX) is themaximum heater power, R_(HEATER) is the nominal resistance of the heaterelement 2000, and V_(rms) is the supplied voltage as measured by theVoltage Detect 2020. Another example of the calculation is:PWM _(MAX) =P _(MAX)/(I ² *R _(HEATER))where I is the current flow through heater when the voltage is applied.The controller 2035, after setting the maximum PWM duty cycle, thenvaries the PWM duty cycle of the PWM element 2010 to control thetemperature of the heater pan 142 as measured by a temperature sensor2007. The controller may control the PWM element to achieve a desiredtemperature in a number of ways, including, for example, a PID feedbackloop, or a PI feedback system.

In an alternative method and configuration, the PWM circuit 2005 doesnot include the voltage detect 2020. In this alternative method thecontroller 2035 varies the PWM duty cycle of the PWM element 2010 toachieve the desired heater pan temperature as measured by temperaturesensor 2007. The controller 2035 begins the heating cycle at a minimumPWM duty cycle and increases the PWM duty cycle until the temperaturesensor reports the desired temperature to the controller 2035. The rateof increase of the PWM rate may be limited or controlled to avoidexcessive currents that could trip and blow the fuses 2050. Thecontroller 2035 may alternatively use small gains in a feedbackcalculation to limit rate of PWM duty cycle increase. Alternatively thecontroller may use a feed forward control to limit the rate of PWM dutycycle increase.

Dual-Voltage Heater Circuit

An example of a dual-voltage heater circuit 2012 that changes theresistance of the heater is shown as a schematic block diagram in FIG.143. The block diagram in FIG. 143 presents one example of adual-voltage heater circuit 2012 to provide approximately constantheater power for the two standard AC voltages of 110 and 220 volts rms.Dual-voltage heater circuit 2012 limits the maximum current flow byreconfiguring the heater and thus is less sensitive to software errorssetting the duty cycle of the PWM element as in circuit 2005. Circuit2012 lowers the maximum current flows through the PWM element 2010 whichallows for smaller and less expensive SSRs. The selection of the heaterconfiguration in circuit 2012 is separated from the heater modulation toimprove control and reliability. The PWM elements 2010A, 2010B thatmodulate the heater power are typically SSR, which typically failclosed, thus providing maximum power. The heater select relay 2014 maybe an electromechanical relay, which while less than ideal for highcycle applications, may typically be preferred for safety criticalcircuits, due in part to the tendency of electromechanical relays tofail open. The selection of the heater configuration by the processorallows more control of heater configuration.

In the event of the AC Mains voltage fluctuating, perhaps due to abrown-out, the controller preferably holds the heater configurationconstant. In contrast, a circuit that automatically changes the heaterconfiguration based on the instantaneous voltage could fluctuate betweenheater configurations. This may result in high current flows if thecircuit does not respond fast enough to line voltage that returns to itsoriginal level from a temporarily lower level. This is more likely to bea problem when only a hardware-enabled circuit is used to respond tovoltage fluctuations. A more efficient and reliable solution may beobtained if a programmable controller is used to either analyze thelikely cause of the input voltage fluctuation, or to respond only to themeasured current flow through the heater averaged over a period of time.In an embodiment, the processor receives input from the user or patientin selecting the heater configuration (parallel or series), and thedual-voltage heater circuit 2012 does not automatically switch betweenconfigurations in response to fluctuating line voltage. In anotherembodiment, the processor measures the current flow in the seriesconfiguration (i.e. the higher resistance configuration) at full power,selects a heater configuration appropriate to the AC mains voltage atthe start of therapy, and does not change configuration for the durationof therapy.

The dual-voltage heater circuit 2012 may comprise two heater elements2001, 2002 that can be connected in parallel or in series with oneanother to provide the same heater power for two different voltages atthe AC mains 2040. Each heater element 2001, 2002 may comprise one ormore heater sub-elements. The electrical resistance of heater elements2001, 2002 is preferably approximately equal. The controller 2035 mayreceive a signal from the current sense 2022 and control the heaterselect relay 2014 to connect the heater elements 2001, 2002 in eitherseries or parallel. The controller 2035 may change the electricalarrangement of the two heater elements to limit the current flowresulting from different AC mains voltages. One example of a currentsense 2022 is a current sense transformer AC-1005 made by Acme Electric.

The power in the heater elements 2001, 2002 may be further modulated bythe PWM elements 2010A, 2010B controlled by the controller 2035 toachieve a desired temperature as measured by temperature sensor 2007, orto achieve other control goals as described above. The PWM elements2010A, 2010B may be a solid state relays such as MCX240D5® by CrydomInc. The safety relay 2030 may be configured to disconnect the heaterelements 2001, 2002 from the AC mains 2040. The safety relay 2030 may becontrolled by the controller 2035 or another processor or safety circuit(not shown).

The safety relay 2030 and heater select relay 2014 may be solid state orelectro-mechanical relays. In a preferred embodiment, the safety relay2030 and/or heater select relay 2014 are electro-mechanical relays. Oneexample of an electro-mechanical relay is a G2AL-24-DC12 relay made byOMRON ELECTRONIC COMPONENTS and other manufacturers. Electro-mechanicalrelays are often preferred for safety critical circuits as they areconsidered to be more robust and more reliable than solid state relays,and have a tendency to fail open. They may also be less susceptible tovarious failures in the controller software.

In one example, the heater select relay 2014 comprises a double-poledouble-throw relay, in which the outputs connect to the heater elements2001, 2002. The heater select relay 2014, in the non-energized state,connects the heater elements 2001, 2002 in series such that the currentflows through one element and then the other. The series configurationmay be achieved, in one example circuit, by the following; connect thefirst end of the heater element 2001 to L1 circuit 2041 via PWM element2010A; connect the joined ends of heater elements 2001, 2002 to an opencircuit via the first pole 2014A; connect second end of heater element2002 to the L2 circuit 2042 via the second pole 2014B. In an energizedstate, the heater select relay 2014 connects the heater elements inparallel such that approximately half the current flows through each PWMand heater element. The parallel configuration may be achieved in thesame example circuit by the following: connect the first end of theheater element 2001 to L1 circuit 2041 via PWM element 2010A; connectthe second end of heater element 2002 to the L1 circuit 2041 via PWMelement 2010B; connect the joined ends of heater elements 2001, 2002 toL2 circuit 2042 via the first pole 2014A. The preferred circuit connectsthe heater elements 2001, 2002 in series in the unpowered condition asit is a safer configuration because the resulting higher resistance willlimit current flows and avoid overloading the fuses 2050, or overheatingthe heating elements 2001, 2002 if connected to a higher voltage ACmain.

Another example of a heater circuit 2112 that changes the effectiveresistance of the heater by changing the heater configuration is shownin FIG. 144 as a schematic block diagram. The heater circuit 2112 issimilar to heater circuit 2012 (shown in FIG. 143) except that heatercircuit 2112 provides better leakage current protection in the eventthat the L1 and L2 power circuits are reversed at the wall socket. Thereversal of the L1 and L2 power circuits is possible if the power wasincorrectly wired in the building that supplies power to the heatercircuit. Wiring in a residential building may not be as reliable as ahospital, where all the electrical system is installed and maintained byqualified personnel.

The electrical components and connections between the PWM elements2010A, 2010B, the nominal L1 circuit 2041, heater elements 2001, 2002,heater select relay 2014 and the nominal L2 circuit 2042 in heatercircuit 2112 are arranged to minimize leakage current regardless of wallsocket polarity. In the non-energized state as shown in FIG. 144, theheater select relay 2014 connects the heater elements 2001, 2002 inseries with the PWM element 2010A. One possible circuit that connectsthe heater elements in series includes: the first end of heater element2001 connected to the L1 circuit 2041 via PWM element 2010A; the secondend of heater element 2001 connected to the first end of heater element2002 via the first pole 2014A, a L1 2014C and the second pole 2014B; andthe second end of heater element 2002 connected to the L2 circuit 2042via PWM element 2010B. In the energized state, the heater elements 2001,2002 and PWM elements 2010A, 2010B are connected in parallel. In anenergized state, the heater select relay 2014 connects the heaterelements in circuit 2122 in parallel such that approximately half thecurrent flows through each PWM and heater element. One possible circuitto connect the two heater and PWM elements in parallel includes: thefirst end of heater element 2001 connected to the L1 circuit 2041 viaPWM element 2010A; the second end of heater element 2001 connected viathe first pole 2014A to the L2 circuit; the first end of heater element2002 is connected to the L1 circuit 2041 via the second pole 2014B; thesecond end of heater element 2002 is connected to the L2 circuit 2042via the PWM element 2010B. The safety relay 2030 is located on the L2circuit 2042 and creates a fail-safe condition of no current flow byopening if a fault occurs. The control of the safety relay is describedbelow. The controller 2035 controls the heater configuration to limitthe current flow as measured by the current sense 2022 to levels belowthe current rating for the fuses 2050, heater elements 20001, 2002, thePWM elements 2010A, 2010B and limits total heater power. The controller2035 varies the duty cycle of the PWM elements 2010A, 2010B to controlthe heater pan 142 temperature as measured by the sensor 2007.

Dual-Voltage Heater Circuit Implementation

A circuit diagram 2212 of one embodiment of the present invention isshown in FIG. 145, which is equivalent to heater circuit 2012 in FIG.143. In the circuit 2212, the heater elements 2001, 2002 are connectedin series by the heater select relay 2014 when the relay coil 2014D isnot energized. The controller (not shown) connects the heater elements2001, 2002 and PWM elements 2010A, 2010B in parallel by supplying asignal at node 2224, which closes transistor switch 2224A, andenergizing the relay coil using the Vs DC power 2214. The controllermodulates the heater power by varying the duty cycle of the PWM elements2010A, 2010B through a signal at node 2220 and powered with Vsupply2210. The current flow is measured with the current sense 2022. Thesafety relay 2030 is normally open. The safety relay 2030 may becontrolled by an FPGA board that is separate from the controller. TheFPGA board monitors the operation of the APD cycler, including theheater pan temperature and the current sense and several otherparameters. The FPGA board may open the relay by removing the signal atnode 2228. The safety relay coil 2030D is powered by the Vsafety 2218.

In one example, the voltage supplying Vsupply 2210, Vs 2214, Vsafety2218 may be the same voltage source. In another example each voltagesource be controllable to provide additional operation control of theheater circuit for added safety. In one example the Vsafety 2218 may becontrolled by multiple processors in the APD cycler 14. If any of theprocessors detects an error and fails, then the Vsafety circuit isopened, the Safety Relay 2030 is opened and heater power is turned off.

Dual-Voltage Heater Circuit Operation

In a typical dual-voltage scenario, a user may wish to use theperitoneal dialysis cycler in either a 110 volt environment or a 220volt environment (i.e. in most cases a 100% difference in voltage towhich the device may be exposed). More generally, however, thedual-voltage heater circuit can be configured for any scenario in whicha first voltage and a second higher voltage may be used. The circuitswitching system would only be limited by the ability of the controllerto discriminate between the current flows resulting from a first voltageor a second voltage being applied to the heater. The elements of thesystem can include a heater comprising a first heater element connectedto a second heater element by a heater select relay, the heater selectrelay being configured to connect the first heater element either inseries or in parallel with the second heater element. A current senseelement is configured to measure current flow through the heater. Acontroller can then be configured to receive the current flowinformation from the current sense element, and command the heaterselect relay to switch to either a parallel or series configuration tomore closely approximate a current flow that has been pre-determined toprovide an optimal degree of heater function and responsiveness. In mostcases, it may be safer to have the cycler power up for initial use in adefault mode with the heater select relay in a series configuration.

The heater circuit is operated to provide adequate heater power withoutallowing damaging currents to flow through the heater elements 2001,2002 or the fuses 2050. The heater circuit 2212 may be configured beforethe therapies are run on the APD cycler 14 and not changed duringoperation regardless of the voltage changes in the AC mains. The controlsystem 16 (in FIG. 127) starts up the heater control circuit 2212 withthe heater select relay 2014 un-energized, so the heater elements areconnected in series to minimize the current. As one part of the startupprocesses, software in the automation computer 300 may run a currentflow test of the heaters by commanding the PWM elements 2010A, 2010B to100% duty cycle and the resulting test current is measured by thecurrent sense 2022 and communicated to the automation computer 300. Theduty cycle of the PWM elements 2010 may be reset to zero after currentflow test.

In one example method, the automation computer 300 evaluates themeasured test current against a predetermined value. If the measuredtest current is above a given value, the automation computer 300 willproceed with the ADP cycler startup procedure. If the measured testcurrent value is below that same given value, then the automationcomputer 300 will energize the heater select relay to reconfigure theheater elements 2001, 2002 in parallel. The current flow test isrepeated and if the new measured test current is above the predeterminedvalue the automation computer 300 will proceed with the ADP cyclerstartup procedure. If the measure test current from the current flowtest with parallel heater elements, is below above the predeterminedvalue, the automation computer 300 will signal an error to the userinterface computer 302.

Alternatively, the automation computer 300 may calculate a test voltagebased on the measured test current and heater element configuration. Ifthe test voltage is in the range of 180 to 250 volts rms, then theautomation computer 300 will proceed with the ADP cycler startupprocedure. If the test voltage is in the range of 90 to 130 V rms, thenthe automation computer 300 will energize the heater select relay toreconfigure the heater elements 2001, 2002 in parallel, repeat thecurrent flow test, and recalculate the test voltage. If the test voltageis in the range of 90 to 130 V rms, the automation computer 300 willproceed with the ADP cycler startup procedure, if not automationcomputer 300 will signal an error to the user interface computer 302.

In another example method, the automation computer 300 compares themeasured test current with the heater elements configured in series to aseries-low-range and series-high-range of current values. Theseries-low-range is consistent with a low AC voltage flowing through theheater elements arranged in series. The series-high-range is consistentwith a high AC voltage flowing through the heater elements arranged inseries. In an exemplary embodiment, the low AC voltage includes rmsvalues from 100 to 130 volts, while the high AC voltage includes rmsvalues from 200 to 250 volts.

If the measured test current is outside of low-range and the high-range,then the automation computer 300 may determine that the heater circuitis broken and signal an error to the user interface computer 302. If themeasured test current is within the high-range, the heater configurationis left unchanged and the startup of the APD cycler 14 may continue. Ifthe measured test current is within the low-range and the heaterelements are arranged in series, then the automation computer 300 mayreconfigure the heater elements 2001, 2002 to a parallel arrangement byenergizing the heater select relay 2014 through a signal at node 2224.The automation computer 300 may control the heater select relay 2014 viaa command sent to the hardware interface 310 that in turn provides thesignal to actuate the heater select relay 2014.

The automation computer 300 may repeat the current flow test afterreconfiguring the heater elements into a parallel arrangement by againcommanding the PWM elements 2010A, 2010B to 100% duty cycle andmeasuring the current flow with the current sense 2022. The measuredtest current may be evaluated against the parallel-low-range of currentvalues. If the measured test current is within the parallel-low-rangevalues proceed with the ADP cycler startup procedure. If the newlymeasured test current is outside the parallel-low-range values, thenautomation computer 300 will signal an error to the user interfacecomputer 302.

The FPGA controller implemented in the hardware interface 310 may beprogrammed to command the safety relay 2030 to open through a signal atnode 2228 while the heater select relay 2014 is switched. The safetyrelay 2030 may be opened each time the heater select relay 2014 isopened or closed to prevent a short circuit from one pole to the otherwithin the heater select relay 2014.

Dual-Voltage Heater Circuit Operation with User Input

In an alternative embodiment, the automation computer 300 may requireuser intervention before reconfiguring the heater elements 2001, 2002.Requiring user input provides a valuable safety feature of oneembodiment of the present invention. FIG. 146 shows a logic flow chartillustrating a method 2240 to include the user in configuring the heaterelements appropriately for the available AC voltage. In step 2241, thecontrol system 16 (in FIG. 127) starts up the heater control circuit2212 (FIG. 145) with the heater select relay 2014 un-energized, so theheater elements are connected in series to minimize the current. Insetup 2242, the automation computer 300 commands the PWM elements 2010A,2010B to 100% duty cycle and the current is measured by the currentsense 2022 and the measure test current is communicated to theprocessor. The duty cycle of the PWM elements 2010 may be reset to zeroafter the test current is measured. In step 2244, the automationcomputer 300 compares the measured test current to a first range. Instep 2245, if the measured test current is within the first range, thenthe heater configuration is correct and the APD operation proceeds instep 2254. In an alternative embodiment, method 2240 includes step 2245Awhere the user interface computer 302 ask the user to confirm the ACmains voltage that the automation computer 300 determined from measuredtest current and the heater configuration before proceeding from step2245. If the user does not confirm the AC voltage level, method 2240will proceed to step 2252 and displays an error.

In step 2246, if the measured current is outside the second range, thenmethod 2240 displays an error in step 2252, otherwise the method 2240proceeds to step 2247. In step 2247, if the user confirms low AC voltagethen the heater configuration will be changed in step 2248, otherwisethe method 2240 displays an error in step 2252. In step 2248, theautomation computer 300 reconfigures the heater elements 2001, 2002 to aparallel arrangement by energizing the heater select relay 2014 througha signal at node 2224. After reconfiguring the heater elements in step2248, the method 2240 retests the heater in step 2242 and continuesthrough the logic flow chart of method 2240.

An alternative embodiment, a user or patient may store the AC voltage ashigh or low in the memory of the control system 16 so that theautomation computer 300 need not query the user or patient at eachtreatment to confirm the AC voltage. FIG. 147 shows a logic flow chartillustrating a method 2260 where the AC voltage value is stored in thememory of the control system 16. The steps 2241 through 2246 are thesame as method 2240 described above. In step 2249, the memory is queriedfor the stored AC voltage value. If the stored AC voltage value is low,then the method 2260 proceeds to step 2248 and reconfigures the heaterelements into a parallel arrangement. If the stored AC voltage is highnor zero, then the user interface computer 302 may query the user toconfirm a low AC mains voltage. If a user confirms the low AC voltage,then the method 2260 proceeds to step 2248 and reconfigures the heaterelements into a parallel arrangement. Step 2248 may also include thesetting the stored AC voltage to low. After reconfiguring the heaterelements in step 2248, the method 2260 retests the heater in step 2242and continues through the logic flow chart of method 2260.

In one example, method 2260 may include a step 2245A which reads frommemory or calculates the test voltage from the measured test current andheater configuration and then has the user interface computer 302 asksthe user to confirm the test voltage. The method may include a stepbetween 2245 and 2246, where if the heater has been reconfigured to aparallel arrangement and the current is not within the high range, thenthe method proceeds to step 2252 and shuts down the APD cycler 14.

The methods 2240 and 2260 may evaluate the measured test current by anumber of different methods. A preferred method was described above andalternative examples are as are described below. The first range in step2245 may be a range of current levels that would provide the desiredamount of maximum heater power for the current heater elementconfiguration. Alternatively step 2245 may calculate a test voltage fromthe measured test current and heater element configuration and evaluateif the test voltage is correct for the heater configuration:approximately 110 V rms for parallel configuration and approximately 220V rms for series configuration. Alternatively step 2245 may test if themeasured test current is above a given predetermined value. The secondrange in step 2246 may be a range of current values corresponding toapproximately 110 V rms in a series configuration. Alternatively step2246 may calculate a test voltage from the measured test current andheater element configuration and evaluate if the test voltageapproximately 110 V rms for a series configuration. Alternatively, step2246 may evaluate if the measure test current is below a givenpredetermined value.

In another embodiment, the selected AC voltage value in method 2260 maybe preloaded in the factory or distribution center based on the expectedlocation of usage. For example, the AC voltage value may be selected forlow if the APD cycler will be used in the US, Canada or Japan. Foranother example, the AC voltage value may be selected for high if theAPD cycler will be used in Europe, or Asia.

For machines expected to operate in a given region, this database may beas simple as a regional voltage being loaded on the machine at thefactory, or loaded by a technician during initial set-up at a place ofoperation. These regional AC voltage value prescriptions may be enteredmanually, using a memory stick or similar device, using a personal datakey (PDK), a compact disc, bar code reader over the world wide web usingan Ethernet or wireless connection or by any other data transfermechanism obvious to one skilled in the art. In other embodiments, setsof regional voltages may be accessible to control system 16 and may beused to inform a user of the typical operating voltage in his or herarea. In one embodiment, prior to accepting a user input in step 2247 tochange voltage from a previous setting, a user would be informed of thetypical voltage of a region; thus a user unfamiliar with the value ofregional voltages would only be required to know his or her currentlocation to provide a safeguard against voltage incompatibility.

In another embodiment, APD cycler 14 would be equipped with a mechanismto determine its current location, for example a GPS tracker, anEthernet connection and a mechanism to determine the location of theconnection, or a mode where user interface 302 can be used to enter thepresent location, such as country or continent. In an embodiment, afterstarting up in a series heater configuration and running a current flowtest, a user may simply be queried as to his or her present location; ifthe response to that query matches both the voltage associated with themeasured test current and heater configuration and the typical voltagefor that region, then treatment is allowed to proceed.

In one embodiment of the present invention a manual switch (not shown),or alternately a logic switch, is used to set the APD machine to theappropriate, safe voltage for use. The instantaneous voltage is measuredand this measurement, either as the specific value or as a categoricaldescriptor, is displayed to the user. The user must respond that themeasured voltage is within the safe operating range for the machine ascurrently configured, or alternately must respond by altering theconfiguration of the machine, before power is allowed to flow to theheating element. The configuration could be altered electronically, forexample via the user interface computer 302, or could be performedmanually by flipping a switch.

In another embodiment of the present invention, a rectifier converts anyincoming alternating current (AC) into a single direct current (DC). Theheater circuit would resemble heater circuit 2005 in FIG. 140 except thevoltage detect 2020 element is replaced with a universal DC supply thatrectifies the AC voltage into a selected DC voltage. The electricalpower supplied to the heater elements 2001, 2002 may be modulated by aPWM element in the rectifier or by a separate PWM element 2030. Theheater circuit may include a safety relay 2010. The single voltage DCpower source allows the use of one heater configuration. The PWM element2030 in this embodiment may comprise one or more IGBT or an MOSFETswitches and related electrical hardware. In a preferred embodiment, theincoming alternating current would be converted to direct current in therange of 12V to 48V.

In another embodiment, the heater element 2000 may comprise a PositiveTemperature Coefficient (PTC) element that self limits the powerdissipated. The internal electrical resistance of a PTC elementincreases with temperature, so the power level is self limiting. PTCheater elements are commercially available from companies such as STEGOthat are rated to run on voltages from 110 to 220 V rms. A heatercircuit employing a PTC heating element would resemble heater circuit2005 with the voltage detect element 2020 removed. The heater powerwould be controlled with the PWM element 2010 using a Triac.

Additional Heater Circuit Embodiments

In another embodiment of the dual voltage heater circuit, the heaterelements are separated from both lines of the AC mains by modulatingswitches. This embodiment may also comprise AND circuitry that closesthe modulating switches only when both a first controller and a secondcontroller enable the modulating switch. The first controller may sendPWM signals to the modulating switches in order to control theelectrical power delivered to the heater elements. The second controllermay enable the modulating switches if the PD system is operating in anacceptable manner. The second controller may disable the modulatingswitches if an alert or an alarm or an unsafe condition exits. The ANDcircuitry that allows control of the modulating switches removes theneed for separate safety relays. This embodiment may include a voltageselector switched that may be controlled with a signal from thecontroller, or a external switch controlled by the user, or a jumperwire for manual switching.

FIG. 148 depicts an example heater circuit 2930 which may be included inany fluid handling device, such as an automated peritoneal dialysismachine. The example heater circuit 2930 depicted in FIG. 148 includesan adaptive or reconfigurable heater element 2917 which may beconfigured to operate at a plurality of voltages while still producingapproximately the same heat output. Additionally, the heater circuit2930 provides enhanced leakage protection even in the event that theline and neutral wires are reversed at a wall socket.

As shown, the heater circuit 2930 in FIG. 148 includes a controller2904. The controller 2904 may control various components of the heatercircuit 2930. In some embodiments, the controller 2904 may include oneor more processors. For example, the controller 2904 may include acontrol processor and a safety processor which is independent of thecontrol processor. The controller 2904 may control the temperature of aheater pan 2914 by selectively connecting a line end of the AC mains2900 to a heater element 2917 and enabling current flow through theheater element 2917. In the example embodiment, the heater element 2917includes a set of two resistive elements 2918A, 2918B. In otherembodiments, the heater element 2917 may include more than two resistiveelements, or additional sets of resistive elements. Additionally, eachresistive element, may in some embodiments include one or a number ofsub elements.

As shown, the configuration of the resistive elements 2918A, 2918B ofthe heater element 2917 is alterable by means of a heater select relay2920. The heater select relay 2920 may be controlled by means of asignal from the controller 2904. In the example embodiment in FIG. 148,the heater select relay 2920 is depicted as a double-pole double-throwrelay. The heater select relay 2920 may be an electromechanical relay ora solid state relay. Since the heater select relay 2920 will be switchedrelatively infrequently (e.g., only at startup), it may be desirable touse an electromechanical relay.

In a non-energized state (shown in FIG. 148) the heater select relay2920 may configure the heater element 2917 such that its resistiveelements 2918A, 2918B are in series with one another. Thisconfiguration, being a higher resistance configuration, may be used whenthe AC mains 2900 is supplying power to the device at a higher voltage(e.g. 230V). In other embodiments, this may be a default configurationfor safety reasons at start-up of the device. Preferably, thenon-energized state of the heater select relay 2920 is configured tohave the resistive elements 2918A, 2918B in series. This seriesconfiguration is most limiting of current flow through the resistiveelement 2918A, 2918B, since upon start-up, the incoming AC mains 2900voltage may not be known, or measured, or pre-set. If the controller2904 of the heater circuit 2930 is configured to determine the properconfiguration of the heater element 2917 after the device has beenturned on (either through measurement of the source, or through queryingof the user, or through detection of the shape or configuration ofelectrical plug in use), then the set of resistive elements 2918A, 2918Bpreferably is configured in series when the device is turned on.

As shown, the heater circuit 2930 includes a current sense element 2906.Such an element may be used to determine the amount of current flowthrough the heater element 2917. A signal from the current sense element2906 may be provided to the controller 2904. In some embodiments, thesignal from the current sense element 2906 may be routed through varioustypes of circuitry for amplification or filtering purposes.

Depending on the amount of current flow through the heater element 2917,the configuration of the heater select relay 2920 may be changed. Insome embodiments, if the current sense element 2906 detects a currentflow below a predetermined threshold, the heater select relay 2920 mayalter the configuration of the heater element 2917. If the current senseelement 2906 detects a current flow above the predetermined threshold,the heater select relay 2920 may keep the heater element 2917 in itscurrent configuration.

In some embodiments, additional thresholds may be employed. There may,for example, be a no current flow threshold, or parallel configurationfault threshold. Such a series fault or no current threshold may be usedto detect a fault condition when, for example, the heater element 2917is commanded to be on. For example, in a scenario in which a thermalfuse has blown, an open circuit may be present and no current may flowthrough the heater element 2917. In the event that current flow isdetermined to be below the no current flow threshold, the heater selectrelay 2920 may be kept in its current configuration and the controller2904 may disable the heater element 2917. Additionally, in such ascenario, the device may notify a user that a fault condition exists. Aparallel configuration fault threshold may be set to detect a scenarioin which the heater element 2917 is configured in parallel and one ofthe resistive elements 2918A, 2918B is non-functional (e.g. its thermalfuse has blown). In the event that the current sense element 2906detects a current indicative of such a situation, the device may notifya user that a fault condition exists. In some embodiments, the therapymay optionally be allowed to continue. In this case, the notificationmay indicate to the user that the therapy may include fewer cycles as itwill take longer for fluid in a heater bag to be heated by only a singleresistive element 2918A, 2918B.

In alternate embodiments, other logic, such as any of the logicdescribed above, may be employed by the controller 2904 to determinewhen and if the heater select relay 2920 should alter the heater element2917 configuration.

Preferably, the heater element may be reconfigured by the controlleronly once each time the device is turned on. Additionally, thecontroller 2904 may preferably disable the heater element 2917 whenswitching the heater select relay 2920 In the example embodiment shownin FIG. 148, this may, for example, be accomplished by switching bothpulse width modulated elements 2908, 2910 off.

A current sense element 2906 may also be used advantageously for otherapplications. The current sense element 2906 may be used upon startup orduring pre-therapy to assess whether a heater element 2917/heatercircuit 2930 is functioning properly. For example, to ensure that anenable signal for the heater element 2917 is not stuck on, thecontroller may set the enable signal to off while commanding the heaterelement 2917 to operate at 100% duty cycle. In embodiments where anenable signal is used, when the enable signal set to off, the heaterelement 2917 should not be powered regardless of the commanded dutycycle. Instead of monitoring temperature sensor data from one or moretemperature sensor associated with the heater pan 2914 to determine ifheating is occurring, the current sense element 2906 may be monitored.In the event that current is flowing through the heater element 2917, itmay be determined that a fault condition exists. This may allow for areliable determination of whether or not such a fault exists to be madequickly. When relying on the temperature sensors, time must be allottedduring the test for the heater pan 2914 to warm up. Such a warm up timeis not necessary if a current sense element 2906 is monitored instead.It should be noted that the current sense element 2906 may, for example,also be used during startup to determine that the heater element 2917draws current when the controller 2904 commands the heater element 2917to be powered. In the event that the heater element 2917 does not drawcurrent when the heater element 2917 is commanded to be powered, a faultcondition may be signaled. Upon determination of the above faults, theuser may be notified that the fault condition exists.

In embodiments in which a heater element 2917 may not be reconfigured,or may only be reconfigured manually (e.g. by means of a jumper on acircuit board), including a current sense element 2906 in a heatercircuit 2930 may also be advantageous. For example, the current senseelement 2906 may be monitored to ensure that the AC mains 2900 issupplying the intended voltage for the configuration. In the event thatthe current sense element 2906 indicates that the AC mains 2900 is notat the intended voltage, the device may be configured to notify a userand may cut power to the heater element 2917 depending on the AC mains2900 voltage. For example, if the heater element 2917 is configured for120V operation, the current sense element 2906 may be monitored todetermine that the current flow is not indicative that the AC mains 2900is supplying 230V. In the event that the current sense element 2906detects that a heater element 2917 configured for 120V is receivingpower from a 230V AC mains 2900, the heater element 2917 may be disabledby a controller 2904. Additionally, the device may notify the user (e.g.via the user interface) that the device is connected to the incorrectmains voltage. If the heater element 2917 is configured for 230Voperation, the current sense element 2906 may be monitored to determinethat the current flow is not indicative that the AC mains 2900 issupplying 120V. In the event that the current sense element 2906 detectsthat a heater element 2917 configured for 230V is receiving power from a120V AC mains 2900, the device may notify the user (e.g. via the userinterface) that the device is connected to the incorrect mains voltage.In this scenario, the user may be allowed to continue with the therapy,however, the notification provided to the user may inform the user thatthe therapy is likely to include fewer cycles because the heater element2917 may be unable to heat fluid in a heater bag as quickly as if theheater element 2917 was its intended AC mains 2900 voltage.

As mentioned above, the controller 2904 may control the temperature ofthe heater pan 2914 by selectively connecting the AC mains 2900 to aheater element 2917 and enabling current flow through the heater element2917. In the example embodiment, this selective connection may beestablished by means of a pulse width modulated element (e.g., solidstate relay) 2908, 2910. The pulse width modulated element 2908, 2910may be any suitable type of switch capable of switching large currentflows off/on multiple times a second. In a preferred embodiment, thepulse width modulated element 2908, 2910 is a solid state relay. In suchembodiments, the pulse width modulated element 2908, 2910 mayspecifically be a TRIAC or a suitable arrangement of silicon controlrectifiers. Preferably, the degree of coupling between the triggeringcircuit and the pulse width modulated element 2908, 2910 should beminimized. In some embodiments, an optical coupler may be used. In suchembodiments each of the pulse width modulated elements 2908, 2910 mayinclude a photo sensitive diode, and may be controlled by modulationcircuitry that lights an LED.

The signal applied to the pulse width modulated element 2908, 2910 bythe controller 2904 may control the duty cycle of the pulse widthmodulated element 2908, 2910. By varying the duty cycle of the pulsewidth modulated element 2908, 2910 the controller 2904 may define theamount of time that the heater element 2917 is on and heating the heaterpan 2914. The controller 2904 may modulate a pulse width modulatedelement 2908, 2910 based on feedback from a number of sensors 2916A,2916B, associated with the heater pan 2914. Though two sensors 2916A,2916B are shown in the example embodiment, various embodiments mayinclude a larger or smaller number of sensors. Additionally oralternatively, the controller 2904 may control the duty cycle of thepulse width modulated element 2908, 2910 using information from thecurrent sense element 2906. In various embodiments, the controller 2904may employ any of the logic described herein to control the heater pan2914 temperature or duty cycle of the pulse width modulated element2908, 2910.

The number of sensors 2916A, 2916B may include a temperature sensor suchas a thermocouple or thermistor or other suitable temperature sensor. Insuch embodiments, the number of sensors 2916A, 2916B may provideinformation related to the temperature of the heater pan 2914. In someembodiments, such sensors 2916A, 2916B may be positioned so as tomeasure the temperature of an object (e.g. a dialysate bag or reservoir)which is resting on the heater pan 2914. In such embodiments, thesensors may be substantially thermally isolated from the heater pan2914. In some embodiments, one or more of the sensors 2916A, 2916B maybe positioned so as to measure the temperature of an object on theheater pan 2914 and one or more of the sensors 2916A, 2916B may bearranged to measure the temperature of the heater pan 2914 itself. Insome specific embodiments, five sensors may measure the temperature ofthe heater pan 2914, and two sensors may be used to measure thetemperature of an object on the heater pan 2914. In such embodiments,the temperature data from the sensors measuring the temperature of theobject on heater pan 2914 may be fed into a control loop controlling thetemperature of the heater pan 2914. In some embodiments, the controlloop may be used to set a target temperature for the heater pan 2914.

The number of sensors 2916A, 2916B may include a pressure sensor in someembodiments. In such embodiments, one or more pressure sensor (s) mayprovide information related to the weight of an object (e.g. dialysatebag or reservoir) which is resting on the heater pan 2914. In someembodiments, the number of sensors 2916A, 2916B may include a sensor orsensors configured to monitor fluid flow into and/or out of an object(e.g. dialysate bag or reservoir) resting on the heater pan 2914.

In an example embodiment, the controller 2904 may modulate a pulse widthmodulated element 2908, 2910 to heat dialysate in a dialysate reservoirresting on the heater pan 2914. The controller 2904 may employ logic toheat the dialysate to within a predetermined temperature range. Thecontroller 2904 may use feedback from the number of sensors 2916A, 2916Bto control heating of the dialysate to within the predeterminedtemperature range, preferably selected to avoid significantly raising orlowering a recipient's body temperature. Selection of the appropriaterange may depend on the mass or volume of fluid to be heated andinfused, either or both of which can be measured and included in acalculation to determine the appropriate temperature range. For example,the mass of fluid may be calculated from a pressure sensor monitoringthe weight of a dialysate reservoir, and the volume of fluid infused maybe determined from FMS measurements of pressure-volume relationships inthe membrane-based pumps.

The heater circuit 2930 shown in FIG. 148 may also include a number ofsafety relays 2912A, 2912B and one or more fuses (or circuit breakers)2902. The safety relays 2912A, 2912B may be controlled by the controller2904 as shown, or may be controlled by a separate controller which isindependent of the controller 2904. The safety relays 2912A, 2912B maybe switched to open circuit in the event that a failure condition isdetected. The safety relays 2912A, 2912B may be any suitable variety ofrelays, for example, solid state relays or electromechanical relays. Insome embodiments, the pulse width modulated elements 2908, 2910 may alsoperform the role of the safety relays 2912A, 2912B. That is, the pulsewidth modulated elements 2908, 2910 and safety relays 2912A, 2912B neednot be separate components. The one or more fuses 2902 may additionallyserve to protect the heater circuit 2930 in the event that a failurecondition occurs. If the fuse 2902 is subjected to an excessive amountof current flow, the fuse 2902 may trip or blow protecting the heatercircuit 2930 from the high current. In some embodiments each of thenominally hot and nominally neutral lines may include a separate fuse2902.

The heater circuit 2930 in FIG. 148 is also arranged such that itminimizes touch or leakage current. The heater circuit 2930 is arrangedsuch that the circuit protects against touch or leakage current even inthe event that the line and neutral wires are reversed at a wall socket.As shown, in the example embodiment there may be a capacitive couplingbetween the heater element 2917 and the heater pan 2914. In the exampleembodiment shown in FIG. 148, this capacitive coupling is illustrated bycapacitor 2926. This capacitive coupling allows a certain amount oftouch or leakage current to exist. To limit leakage current, suitableinsulation or layers of insulation (not shown) may be provided betweenthe heating element 2917 and the heater pan 2914. The insulation may beselected from any number of suitable insulating materials with a lowdielectric constant and high dielectric strength. It should also benoted that the materials selection for the enclosure and any coatingsmay be chosen to aid in minimizing leakage current.

Additionally, the arrangement and subsequent control of the safetyrelays 2912A, 2912B and the pulse width modulated elements 2908, 2910may be configured to aid in the reduction of touch or leakage current.Leakage current between the heater element 2917 and the heater pan 2914will be higher when the heater element 2917 is at a higher voltage. Thusit may be desirable to protect against a situation in which the heaterelement 2917 rests at the full voltage of the AC mains 2900. Such ascenario may occur in the event that the heater element 2917 isconnected to the AC mains 2900 when the heater element 2917 is not on.(i.e. not passing current). A pair of safety relays may be effective inpreventing AC mains voltage from reaching the heater element when theheater is not in use. But during operation of the heater using a PWMsignal, the heater element could be exposed to AC mains voltage duringthe ‘off’ phases of the PWM signal, depending on the polarity of the ACmains connection. By connecting a solid state relay (or PWM element) toboth the first pole and second pole of AC mains (e.g., in a 220 voltsystem), or to both the line wire and neutral wire of AC mains (e.g., ina 110 volt system), commanding the same PWM signal to both solid staterelays effectively ensures that the ‘off’ phases of the PWM signal willreliably isolate the heater element from AC mains voltage regardless ofthe polarity of the AC mains connection. A dual solid state relayarrangement can be used to reduce touch or leakage current moregenerally with any device (e.g., a heater or a motor) having a load thatis powered by high voltage and controlled by a series of on-off (such asPWM) signals. A solid state relay connected to each pole of the highvoltage source and receiving the same control signal can effectivelyreduce the touch or leakage current of the device powered by the highvoltage source.

Situations in which this may occur in a typical 110 volt system includewhen the nominally neutral line provides a closed return path forelectricity provided by the AC mains 2900. This can happen when thenominally neutral line does not include a pulse width modulated element2908, 2910. This can also happen when a pulse width modulated element2908, 2910 on the nominally neutral line is modulated to a 100% dutycycle. In these scenarios, in the event that the polarity of the lineand neutral wires are reversed at the wall outlet, the heater element2917 will rest at the full voltage of the AC mains 2900 when the heaterelement 2917 is off.

By placing a pulse width modulated element 2908, 2910 on both line andneutral legs of the heater circuit 2930 (or, for example on both thefirst and second poles of the AC mains source), such a scenario can beprevented, thus minimizing leakage current due to the capacitivecoupling of the heater element 2917 and the heater pan 2914. As shown,the controller 2904 may be configured to send the same control signal toeach of the pulse width modulated elements 2908, 2910. Thus, the pulsewidth modulated elements 2908, 2910 may be operated in tandem with oneanother at the same duty cycle. In this manner, the heater element 2917can be prevented from resting at the full AC mains 2900 voltage even ifthe polarity of the line and neutral wires are reversed. Controlling thepulse width modulated elements 2908, 2910 in this manner prevents ascenario in which one of the pulse width modulated elements 2908, 2910is in an active state while the other is not. Thus a heater circuit 2930which minimizes leakage current by preventing a heater element 2917 fromresting at the full AC mains 2900 voltage may include a controller 2904,heater element 2917, pulse width modulated elements 2908, 2910 and theAC mains 2900. Heater circuit 2930 may also have other functionalitiesand may include other optional and additional components as shown inFIG. 148.

As shown in FIG. 148, the safety relays 2912A and 2912B may be operatedin tandem by the controller 2904 (or an additional but not showncontroller independent of controller 2904). This may help to backstop asituation, for example, in which a pulse width modulated element 2908,2910 fails in the closed position.

FIG. 149 shows an example graph 2950 depicting leakage current to aheater pan from a heater element over time. As shown, heating begins atabout 50 seconds. This graph 2950 plots leakage current over time in asituation in which the nominally neutral wire provides a closed returnpath for power from the AC mains and the polarity of the circuit isreversed. That is, the nominally neutral wire is actually a line wire orhot wire. As shown, leakage current starts at approximately 68 microampsand rises to 73 microamp at approximately 65 seconds, next thecontroller begins to PWM the heater circuit which results in afluctuating leakage current between a low value of approximately 70microamps when the heater is on and approximately 90-100 microamps whenthe heater is off. This is because the heater is allowed to rest at arelatively high AC mains voltage (e.g. 230V). When the heater is turnedon, the voltage drop across the resistive elements of the heater elementdecreases the amount of current passing through the capacitive couplingbetween the heater element and the heater pan, thus causing the leakagecurrent to drop. As shown, in the example graph 2950 in FIG. 149 leakagecurrent is between about 100 and 90 μA when the heater is off andbetween about 70 and 65 μA when the heater is on.

FIG. 150 shows another example graph 2960 depicting leakage current to aheater pan from a heater element over time. Again, heating begins atabout 50 seconds. This graph 2960 plots leakage current over time in asituation in which both the nominally hot and nominally neutral wiresare modulated in tandem as described above in relation to FIG. 148. Asshown, leakage current in graph 2960 starts at approximately 65microamps and increases to approximately 70 microamps at approximately65 seconds, when the controller begins to PWM the heater. The leakagecurrent then drops to about 44 μA, while the heater is off and returnsto approximately 65 to 70 microamps when the heater is turned on. Whenthe heater is turned on, leakage current is about the same as in graph2950 (FIG. 149). In FIG. 150, when the heater is turned off, however,leakage current is about 44 μA, significantly lower than that of graph2950.

FIG. 151 depicts an example of a heater circuit 2932 wherein a PWMelement or solid state relay 2908, 2910 is placed on each line from theAC mains to better isolate the heater element while the heater power isoff and reduce leakage current to the heater tray 2914 that mayexperience capacitive coupling to the heater elements. The PWM elements2908, 2910 are controlled by both the controller 2904 and a safetycontroller 2934. Each PWM element 2908, 2910 receives a control signalfrom an AND circuit (not shown in FIG. 151) that in turn receivescontrol signals from the controller 2904 and from the safety controller2934. The AND circuit outputs an enable or ‘on’ signal to the PWMelements 2908, 2910 only when it receives an enable command from boththe controller 2904 and the safety controller 2934. Not all componentsdepicted in FIG. 151 are necessary for implementation of the abovesafety system. The components of heater circuit 2932 including the fuse2902, PWM elements 2908, 2910, current sense 2906, heater select relay2920, heater 2917, heater elements 2918A, 2918B, temperature sensors2819A, 2916B and heater tray 2914 are described in greater detail above.

FIG. 151A depicts another example of a heater circuit 2932A. The heatercircuit 2932A shown is similar to that depicted in FIG. 151. The heatercircuit 2932A includes a first controller 2931 and second controller2933. The PWM elements 2908, 2910 are controlled by both the firstcontroller 2931 and a second controller 2933. Each PWM element 2908,2910 receives a control signal from a gating circuit (not shown in FIG.151A) that in turn receives control signals from the first controller2931 and from the second controller 2933. The gating circuit outputs anenable or ‘on’ signal to the PWM elements 2908, 2910 only when itreceives an enable command from both the first controller 2931 and thesecond controller 2933.

Also shown in FIG. 151A is a safety voltage source 2937. In anembodiment, voltage from the safety voltage source 2937 may be requiredfor the PWM elements 2908, 2910 to enable current flow to the heater2917. In some embodiments, a gating circuit may also require voltagefrom a safety voltage source 2937 in order for the PWM elements 2908,2910 to enable current flow to the heater 2917. The safety voltagesource 2937 may be controlled by either the first processor 2931 orsecond processor 2933 as in the example embodiment. Optionally, thesafety voltage source 2937 may instead or additionally be controlled bya dedicated hardware component 2939. This component 2939 may, forexample, monitor for over-voltage conditions. The dedicated hardwarecomponent 2939 may control the safety voltage source 2937 to prevent thePWM elements 2908, 2910 from allowing current flow to the heater 2917.For example, if an over-voltage condition is detected by the dedicatedhardware component 2939, the safety voltage source 2937 may becontrolled to prevent the PWM elements 2908, 2910 from allowing currentflow to the heater 2917.

FIGS. 152 to 157 depict a specific example of the circuit 2930 shown inFIG. 148. Such a circuit may switch the configuration of a heaterelement based on a sensed current flow through the heater element. Thespecific example circuit may also be arranged to minimize leakagecurrent by providing a pulse width modulated element on the nominallyhot side of the heater element as well as the nominally neutral side ofthe heater element and controlling each in tandem with one another. Notethat when the AC mains deliver a nominal 220-230 VAC, the “neutral line”is a second hot line that provides an alternating voltage that is out ofphase with the alternating voltage supplied by the nominally “hot wire”.Herein, the neutral wire or the neutral side of the heater refers to thewire or heater connected to the neutral side of 120 VAC mains or to theout-of-phase side of 220-230 VAC mains.

FIG. 152 depicts an AC mains input 2990 for the example circuit. Traces3000 and 3002 represent the line and neutral wires, here denoted as L1and L2, of the circuit. In the example embodiment, the convention of L1and L2 instead of Line/Hot and Return/Neutral is used to emphasize thatthe leakage current characteristics of the circuit are independent ofthe polarity of L1 and L2. Referring now also to FIG. 153, as shown, theAC mains input 2990 is connected to the AC switch 2292 of the circuit.In the example embodiment this connection is made by AC L1 switch polein 3008 and AC L2 switch pole in 3010. AC L2 switch out 3012 connectsthe power switch 2992 to one end of the heater circuitry 2994 (see FIG.154) of the example circuit. AC L1 switch out 3014 connects the powerswitch 2992 to the other end of the heater circuitry 2994 of the examplecircuit.

As shown in FIG. 154, both AC L1 switch out 3014 and AC L2 switch out3012 are respectively connected to pulse width modulated elements 3013and 3015. In the example embodiment, the pulse width modulated elements3013 and 3015 are solid state relays. In some embodiments, the pulsewidth modulated elements 3013 and 3015 may be solid state relays with azero crossover switching characteristic. Specifically, in the exampleembodiment, the pulse width modulated elements are silicon controlrectifiers. In other embodiments other types of relays may be used. Forexample, in some embodiments, the pulse width modulated elements 3013and 3015 may be TRIACs.

In the example embodiment, a safety voltage from 3071 is shown connectedto the pulse width modulated elements (solid state relays) 3013 and3015. As mentioned above in relation to FIG. 151A, the safety voltagemay be provided from a safety voltage source 2939 (see FIG. 151A). Thepresence of the safety voltage may be necessary for the pulse widthmodulated elements (solid state relays) 3013 and 3015 to enable currentflow to the heater element 3019. In a failsafe condition, a processor ofthe heater system (e.g. processor 2933 of FIG. 151A) or a dedicatedhardware component (see 2939 of FIG. 151A) may prevent the safetyvoltage from reaching the pulse width modulated elements 3013 and 3015.

The pulse width modulated element (solid state relay) 3015 is connectedto a heating element 3019 via heater AC L1 3016. Heater AC L1 3016 maypass through a current sensing element 3017 on its way to the heatingelement 3019. The current sensing element 3017 may be configured tosense current flow through the heating element 3019. In some embodimentsthe current sensing element 3017 may be a current sense transformer. Thecurrent sensing element 3017 and related components will be furtherdescribed later in the specification. Pulse width modulated element 3015may be modulated between an active (on) and inactive (off) state by asignal sent through heater control A 3050. This signal will also befurther described later in the specification.

Pulse width modulated element 3015 is also connected to a heaterconfiguration relay 3026 via heater AC L1 3016. In the exampleembodiment, the heater element 3019 is a heater element consisting of atleast one set of resistive elements that may be arranged either inseries or parallel. In the example embodiment, the heater configurationrelay 3026 is an electromechanical relay. In other embodiments, theheater configuration relay 3026 may be any other suitable type of relay.As shown, the heater element 3019 is configured for series operation. Inseries configuration, heater AC L1 3016 does not connect to the heaterelement 3019 through configuration switch 3028B of the heaterconfiguration relay 3026, but is directly connected to one end of theheater element 3019 as shown. In parallel configuration, bothconfiguration switches 3028A, and 3028B of the heater configurationrelay 2026 would be in the opposite position. In this position, heaterAC L1 3016 would be directly connected to one end of the heater element3019 and connected to another end of the heating element 3019 throughheater configuration relay 3026 and heater AC L1/L2 3024.

In the example embodiment, as shown in series configuration, the pulsewidth modulated element 3013 is connected to the heater element 3019through: AC L2 switch 3032, the heater configuration relay 3026 (viaconfiguration switch 3028B), and heater AC L1/L2 3024. When the heaterelement 3019 is configured for parallel, the pulse width modulatedelement 3013 is connected to the heating element 3019 through: AC L2switch 3032, the heater configuration relay 3026 (via configurationswitch 3028A), and heater AC L2 3020. Pulse width modulated element 3013may be modulated between an active (on) and inactive (off) state by asignal sent through heater control B 3058. This signal will be describedlater in the specification. In the example embodiment the position ofconfiguration switches 3028A, and 3028B of the heater configurationrelay 2026 may be controlled via a signal sent through configurationselect 3078. Alternatively, in some embodiments, the configuration maybe manually set through manual configuration select 3080. For example, ajumper box may be manually placed over a number of pins in order toselect the configuration. Depending on the selected configuration, theheater configuration relay's 2026 configuration switches 3028A, and3028B may be appropriately positioned by energizing or not energizingcoil 3082 of the heater configuration relay 3026. The configurationsignals sent through configuration select 3078 and manual configurationselect 3080 will be further described later in the specification.

FIG. 155 depicts an example of modulation circuitry or gating circuitry,or an ‘AND’ circuit which may be used in the circuit shown from FIG. 152to FIG. 157. As shown, the example modulation circuitry shown in FIG.155 includes a number of switches which may be current controlledswitches. The AND circuit is configured to provide a path to ground forvoltage from 3071 through 3050 when a positive voltage is applied at3040 and at 3042, which are connected to the controller and safetyprocessor respectively. The AND circuit serves to pass the PWM signalfrom the supplying controller (e.g. controller 2904 or safety controller2934 of FIG. 151) to the PWM element 3015 (FIG. 154) only if the otherof the controlling processors is supplying an enable signal. In anexample, the AND circuit serves to pass the PWM signal from thesupplying controller (e.g. controller 2904 or safety controller 2934 ofFIG. 151) to the PWM element 3015 (FIG. 154) only if the safetyprocessor 2934 (FIG. 151) is outputting an enable signal. As shown, theswitches comprise three transistors 3044, 3046, and 3048, which may forexample be MOSFETs. Accompanying pull-up and pull down resistors arealso included. In the example embodiment, transistors 3046 and 3044 arerespectively controlled by signals from a control processor and a safetyprocessor (neither shown). Thus, in order for the heater element 3019(see FIG. 154) to be switched on via heater control A 3050 (see alsoFIG. 154) through transistor 3048, both the control and safetyprocessors must cooperate and command that the heater element 3019should be powered. The signal from the control processor may travel intothe modulation circuitry through control processor heater signal line3040. The signal from the safety processor may travel into themodulation circuitry through safety processor signal line 3042.

The signals from the control processor and safety processor may be basedon logic that incorporates sensor data. For example, the controlprocessor and safety processor may use data from a sensor or sensors,such as a temperature sensor(s) associated with the heater element, todetermine when the heater element should be on or off. Various types ofcontrol logic that may be used for control of a heater element aredescribed elsewhere herein.

In some embodiments, the control and safety processors may send the samesignal to their respective transistors 3046, and 3044. In someembodiments, the control and safety processors may send differentsignals to their respective transistors 3046, and 3044. In a specificembodiment, the control processor (or alternatively the safetyprocessor) may send an enable signal to transistor 3046. The otherprocessor may send a pulse width modulated signal to transistor 3044.Transistor 3048 will allow the heater element 3019 (see FIG. 154) to beswitched on when both the enable signal and pulse width modulated signalcommand that the heater element 3019 should be powered. The pulse widthmodulated (PWM) element 3015 (see FIG. 154), in this example, wouldeffectively be modulated with the pulse width modulated signal appliedto transistor 3044 by the PWM'ing processor. This configuration alsoensures that in an event in which the processors issue conflictingcommands, i.e. a fault condition, the pulse width modulated element 3015(see FIG. 154) does not allow current flow through the heater element3019.

FIG. 156 depicts modulation circuitry or gating circuitry or an ‘AND’circuit that may be used in the example circuit shown from FIG. 152 toFIG. 157. As shown, the example modulation circuitry shown in FIG. 156is similar to that shown in FIG. 155. The AND circuit is configured toprovide a path to ground for voltage from 3071 through 3058 to the PWMelement 3013 (FIG. 154) when a positive voltage is applied at 3040 andat 3042, which are connected to the controller and safety processorrespectively. The AND circuit serves to pass the PWM signal from thesupplying controller (e.g. controller 2904 or safety controller 2934 ofFIG. 151) to the PWM element 3013 (FIG. 154) only if the other of thecontrolling processors is supplying an enable signal. In an example, theAND circuit serves to pass the PWM signal from the supplying controller(e.g. controller 2904 or safety controller 2934 of FIG. 151) to the PWMelement 3013 (FIG. 154) only if the safety processor 2934 (FIG. 151) isoutputting an enable signal. The modulation circuitry includes threetransistors 3052, 3054, and 3056, which may, for example, be MOSFETs.Accompanying pull-up and pull down resistors are also included. In theexample embodiment, transistors 3054, and 3052 are respectivelycontrolled by signals from a control processor and a safety processor(neither shown). Thus, in order for the heater element 3019 (see FIG.154) to be switched on via heater control B 3058 (see also FIG. 154)through transistor 3056, both the control and safety processors mustcooperate and command that the heater element 3019 should be powered.The signal from the control processor may travel into the modulationcircuitry through control processor heater signal line 3040. The signalfrom the safety processor may travel into the modulation circuitrythrough safety processor signal line 3042.

In the example embodiment, the signals applied to control processorheater signal line 3040 and safety processor signal line 3042 in FIG.156 may be identical to the signals applied to control processor heatersignal line 3040 and safety processor signal line 3042 in FIG. 155. Thatis, both pulse width modulated elements 3013 and 3015 (see FIG. 154) maybe pulse width modulated in tandem at the same duty cycle in someembodiments. Consequently, regardless of the polarity of L1 and L2 inthe circuit shown in FIG. 152, there will not be a condition in whichthe heater element 3019 is held at mains voltage. When the heaterelement 3019 is not in the “on” state, the heater element 3019 will notbe connected to the mains voltage source. It should be noted that thisis also true regardless of the configuration of the heater element 3019;whether the heater element 3019 is configured in series or parallel, itwill not be allowed to rest at the mains voltage.

In some embodiments, there may only be a single modulation circuit. Insuch embodiments, the third transistor of the modulation circuit (either3048 or 3056) may control the state of both pulse-width-modulatedelements 3013 and 3015 (see FIG. 154). Additionally, the modulationcircuits shown in FIG. 155 and FIG. 156 may be used to control thepulse-width-modulated elements 3013 and 3015 such that they function assafety relays when necessary. For example, in the event that a failurecondition is detected, the control signals sent by one or both theprocessors may command the pulse-width-modulated elements 3013 and 3015to turn off or into an inactive state.

In both FIG. 155 and FIG. 156, a safety voltage from 3045 is shownconnected to the gating circuitry. As mentioned above in relation toFIG. 151A, the safety voltage may be provided from a safety voltagesource 2939 (see FIG. 151A). In an embodiment, the presence of thesafety voltage may be necessary for the gating circuitry to enable thepulse width modulated elements (solid state relays) 3013 and 3015 (seeFIG. 154) to enable current flow to the heater element 3019. In afailsafe condition, a processor of the heater system (e.g. processor2933 of FIG. 151A) or a dedicated hardware component (see 2939 of FIG.151A) may prevent the safety voltage from reaching the gating circuitry.

FIG. 157 depicts example circuitry which may be included in embodimentsof a heater circuit that include a current sense element 3017 (see FIG.154). The example circuitry depicted in FIG. 157 may be used to processand filter the signal from the current sense element 3017. As shown, thesignal from a current sense element 3017 may be carried by trace 3070and 3074. This signal may be subjected to rectification via a suitablerectifier 3073. The example rectifier 3073 in FIG. 157 is depicted as aquadruple Schottky barrier diode. A voltage limiting element 3072 isalso included. In the example embodiment, the voltage limiting element3072 is depicted as a Zener diode. In the example embodiment, the signalis then passed through a unity gain amplifier 3075. The signal may alsobe subjected to a low pass filter 3077, which may serve to smooth outthe rectified AC signal. In some embodiments the signal may be passedthrough an operational amplifier 3079 for amplification. In one example,the gain of the operational amplifier 3079 can be set at approximately4.4. As shown, in the example embodiment, the signal then may passthrough an additional low pass filter 3081. The signal may then be fedto a controller (not shown) via trace 3076.

In various embodiments, the signal may be subject to different degreesof amplification and filtering. For example, in some embodiments, thesignal may be subjected to additional filtering. In some embodiments,additional filtering, amplification, etc. may be performed on the signalon a separate circuit board (e.g. the board on which the controllerresides). Preferably, the components are selected to keep the signalfrom becoming saturated. In particular, the components are preferablychosen so that the signal will not become saturated at the highestanticipated current the circuit may encounter.

The controller (not shown) can use the signal from trace 3076 to make adetermination about how a heater element 3019 should be configured. Thecontroller can then send a command signal to the heater configurationrelay 3026 (see FIG. 154) based upon this determination. As mentionedabove, this signal may be sent through the configuration select 3078trace.

Database and User Interface Systems

Referring to FIG. 130, the database subsystem 346, also on the userinterface computer 302, stores all data to and retrieves all data fromthe databases used for the onboard storage of machine, patient,prescription, user-entry and treatment history information. Thisprovides a common access point when such information is needed by thesystem. The interface provided by the database subsystem 346 is used byseveral processes for their data storage needs. The database subsystem346 also manages database file maintenance and back-up.

The UI screen view 338 may invoke a therapy log query application tobrowse the therapy history database. Using this application, which mayalternatively be implemented as multiple applications, the user cangraphically review their treatment history, their prescription and/orhistorical machine status information. The application transmitsdatabase queries to the database subsystem 346. The application can berun while the patient is dialyzing without impeding the safe operationof the machine.

The remote access application, which may be implemented as a singleapplication or multiple applications, provides the functionality toexport therapy and machine diagnostic data for analysis and/or displayon remote systems. The therapy log query application may be used toretrieve information requested, and the data may be reformatted into amachine neutral format, such as XML, for transport. The formatted datamay be transported off-board by a memory storage device, direct networkconnection or other external interface 348. Network connections may beinitiated by the APD system, as requested by the user.

The service interface 356 may be selected by the user when a therapy isnot in progress. The service interface 356 may comprise one or morespecialized applications that log test results and optionally generate atest report which can be uploaded, for example, to a diagnostic center.The media player 358 may, for example, play audio and/or video to bepresented to a user.

According to one exemplary implementation, the databases described aboveare implemented using SQLite®, a software library that implements aself-contained, server-less, zero-configuration, transactional SQLdatabase engine.

The executive subsystem 332 implements two executive modules, the userinterface computer (UIC) executive 352 on the user interface computer302 and the automation computer (AC) executive 354 on the automationcomputer 300. Each executive is started by the startup scripts that runafter the operating system is booted and includes a list of processes itstarts. As the executives go through their respective process lists,each process image is checked to ensure its integrity in the file systembefore the process is launched. The executives monitor each childprocess to ensure that each starts as expected and continue monitoringthe child processes while they run, e.g., using Linux parent-childprocess notifications. When a child process terminates or fails, theexecutive either restarts it (as in the case of the UI view) or placesthe system in fail safe mode to ensure that the machine behaves in asafe manner. The executive processes are also responsible for cleanlyshutting down the operating system when the machine is powering off.

The executive processes communicate with each other allowing them tocoordinate the startup and shutdown of the various applicationcomponents. Status information is shared periodically between the twoexecutives to support a watchdog function between the processors. Theexecutive subsystem 332 is responsible for enabling or disabling thesafe line. When both the UIC executive 352 and the AC executive 354 haveenabled the safe line, the pump, the heater, and the valves can operate.Before enabling the lines, the executives test each line independentlyto ensure proper operation. In addition, each executive monitors thestate of the other's safe line.

The UIC executive 352 and the AC executive 354 work together tosynchronize the time between the user interface computer 302 and theautomation computer 300. The time basis is configured via a batterybacked real-time clock on the user interface computer 302 that isaccessed upon startup. The user interface computer 302 initializes theCPU of the automation computer 300 to the real-time clock. After that,the operating system on each computer maintains its own internal time.The executives work together to ensure sufficiently timekeeping byperiodically performing power on self tests. An alert may be generatedif a discrepancy between the automation computer time and the userinterface computer time exceeds a given threshold.

FIG. 158 shows the flow of information between various subsystems andprocesses of the APD system. As discussed previously, the UI model 360and cycler controller 362 run on the automation computer. The userinterface design separates the screen display, which is controlled bythe UI view 338, from the screen-to-screen flow, which is controlled bythe cycler controller 362, and the displayable data items, which arecontrolled by the UI model 360. This allows the visual representation ofthe screen display to be changed without affecting the underlyingtherapy software. All therapy values and context are stored in the UImodel 360, isolating the UI view 338 from the safety-critical therapyfunctionality.

The UI model 360 aggregates the information describing the current stateof the system and patient, and maintains the information that can bedisplayed via the user interface. The UI model 360 may update a statethat is not currently visible or otherwise discernable to the operator.When the user navigates to a new screen, the UI model 360 provides theinformation relating to the new screen and its contents to the UI view338. The UI model 360 exposes an interface allowing the UI view 338 orsome other process to query for current user interface screen andcontents to display. The UI model 360 thus provides a common point whereinterfaces such as the remote user interface and online assistance canobtain the current operational state of the system.

The cycler controller 362 handles changes to the state of the systembased on operator input, time and therapy layer state. Acceptablechanges are reflected in the UI model 360. The cycler controller 362 isimplemented as a hierarchical state machine that coordinates therapylayer commands, therapy status, user requests and timed events, andprovides view screen control via UI model 360 updates. The cyclercontroller 362 also validates user inputs. If the user inputs areallowed, new values relating to the user inputs are reflected back tothe UI view 338 via the UI model 360. The therapy process 368 acts as aserver to the cycler controller 362. Therapy commands from the cyclercontroller 362 are received by the therapy process 368.

The UI view 338, which runs on the UI computer 302, controls the userinterface screen display and responds to user input from the touchscreen. The UI view 338 keeps track of local screen state, but does notmaintain machine state information. Machine state and displayed datavalues, unless they are in the midst of being changed by the user, aresourced from the UI model 360. If the UI view 338 terminates and isrestarted, it displays the base screen for the current state withcurrent data. The UI view 338 determines which class of screens todisplay from the UI model 360, which leaves the presentation of thescreen to the UI view. All safety-critical aspects of the user interfaceare handled by the UI model 360 and cycler controller 362.

The UI view 338 may load and execute other applications 364 on the userinterface computer 302. These applications may perform non-therapycontrolling tasks. Exemplary applications include the log viewer, theservice interface, and the remote access applications. The UI view 338places these applications within a window controlled by the UI view,which allows the UI view to display status, error, and alert screens asappropriate. Certain applications may be run during active therapy. Forexample, the log viewer may be run during active therapy, while theservice interface and the remote access application generally may not.When an application subservient to the UI view 338 is running and theuser's attention is required by the ongoing therapy, the UI view 338 maysuspend the application and regain control of the screen and inputfunctions. The suspended application can be resumed or aborted by the UIview 338.

FIG. 159 illustrates the operation of the therapy subsystem 340described in connection with FIG. 130. The therapy subsystem 340functionality is divided across three processes: therapy control;therapy calculation; and solution management. This allows for functionaldecomposition, ease of testing, and ease of updates.

The therapy control module 370 uses the services of the therapycalculation module 372, solution management module 374 and machinecontrol subsystem 342 (FIG. 130) to accomplish its tasks.Responsibilities of the therapy control module 370 include trackingfluid volume in the heater bag, tracking fluid volume in the patient,tracking patient drain volumes and ultra filtrate, tracking and loggingcycle volumes, tracking and logging therapy volumes, orchestrating theexecution of the dialysis therapy (drain-fill-dwell), and controllingtherapy setup operations. The therapy control module 370 performs eachphase of the therapy as directed by the therapy calculation module 370.

The therapy calculation module 370 tracks and recalculates thedrain-fill-dwell cycles that comprise a peritoneal dialysis therapy.Using the patient's prescription, the therapy calculation module 372calculates the number of cycles, the dwell time, and the amount ofsolution needed (total therapy volume). As the therapy proceeds, asubset of these values is recalculated, accounting for the actualelapsed time. The therapy calculation module 372 tracks the therapysequence, passing the therapy phases and parameters to the therapycontrol module 370 when requested.

The solution management module 374 maps the placement of solution supplybags, tracks the volume in each supply bag, commands the mixing ofsolutions based upon recipes in the solution database, commands thetransfer of the requested volume of mixed or unmixed solution into theheater bag, and tracks the volume of mixed solutions available using thesolution recipe and available bag volume.

FIG. 160 shows a sequence diagram depicting exemplary interactions ofthe therapy module processes described above during the initial‘replenish’ and ‘dialyze’ portions of the therapy. During the exemplaryinitial replenish process 376, the therapy control module 370 fetchesthe solution ID and volume for the first fill from the therapycalculation module 372. The solution ID is passed to the solutionmanagement module 374 with a request to fill the heater bag withsolution, in preparation for priming the patient line and the firstpatient fill. The solution management module 374 passes the request tothe machine control subsystem 342 to begin pumping the solution to theheater bag.

During the exemplary dialyze process 378, the therapy control module 370executes one cycle (initial drain, fill, dwell-replenish, and drain) ata time, sequencing these cycles under the control of the therapycalculation module 372. During the therapy, the therapy calculationmodule 372 is updated with the actual cycle timing, so that it canrecalculate the remainder of the therapy if needed.

In this example, the therapy calculation module 372 specifies the phaseas “initial drain,” and the therapy control module makes the request tothe machine control subsystem 342. The next phase specified by thetherapy calculation module 372 is “fill.” The instruction is sent to themachine control subsystem 342. The therapy calculation module 372 iscalled again by the therapy control module 370, which requests thatfluid be replenished to the heater bag during the “dwell” phase. Thesolution management module 374 is called by the therapy control module370 to replenish fluid in the heater bag by calling the machine controlsubsystem 342. Processing continues with therapy control module 370calling the therapy calculation module 372 to get the next phase. Thisis repeated until there are no more phases, and the therapy is complete.

Pump Monitor/Math Repeater

The Pump Monitor/Math Repeater process is a software process or functionthat runs on the automation computer 300 separate from the safetyexecutive 354. The Pump Monitor/Math Repeater process is implemented inas two separate threads or sub-functions that run independently. Themath repeater thread, herein referred to as the MR thread, confirms theFMS calculation result. The Pump Monitor thread, referred to as the PMthread, monitors the net fluid and air flow across relevant endpointsfrom information provided in the routine status messages from theMachine process 342. The relevant endpoints may include but not belimited to 5 potential bag spikes, the heater bag, patient port anddrain port. The PM thread will also monitor the heater pan temperaturevia information from the IO Server process. The PM thread will signal analarm to the safety executive 354, if predefined limits for fluid flow,air flow or temperature are exceeded.

The MR thread accepts the high speed pressure data and repeats the FMScalculation described above to recalculate the fluid volume displaced.The MR thread compares its recalculated fluid volume to the volumecalculated by the Machine process 342 and sends a message to the safetyexecutive. In another example, the MR thread declares and errorcondition if the two fluid volume values do not match.

The PM thread monitors several aspects of the pumping process as asafety check on the functioning of the cycler 14. The PM thread willdeclare an invalid pump operation error condition if the HardwareInterface 310 reports valves open that do not correspond to thecommanded pump action by the Machine subsystem 342. An example of aninvalid valve condition would be if any port valve 186, 184 (FIG. 6) areopen, while the pump was in an idle mode. The state of valves in thecassette is mapped to the state of the corresponding pneumatic valves2710, which are energized by the hardware interface 310. Another exampleof an invalid valve condition would be a port valve 184, 186 that isopen that does not correspond to the specified source or sink of fluid.

The PM thread will declare an error condition if excess fluid is pumpedto the patient while the heater button temperature sensor 506 reportsless than a given temperature. In a preferred embodiment, the PM threadwill declare an error condition more than 50 ml of fluid is pumped tothe patient while the button temperature is less than 32° C.

The PM thread will maintain a numerical accumulator on the amount offluid pumped to the patient. If total volume of fluid pumped to thepatient exceeds a specified amount, the PM thread will declare an error.The specified amount may be defined in the prescription information andmay include an additional volume equal to one chamber volume orapproximately 23 ml.

The PM thread will maintain a numerical accumulator on the amount of airmeasured in the pumping chamber by the FMS method for air taken fromeach bag. If the total amount of air from any bag exceeds the maximumallowed volume of air for that bag, then the PM thread will declare anerror. In a preferred embodiment, the maximum allowed air volume for theheater bag is 350 ml and the maximum allowed air volume for a supply bagis 200 ml. A large air volume from a bag indicates that it may have aleak to the atmosphere. The maximum allowed air volume for the heaterbag may be larger to account for out-gassing when the fluid is heated.

Alert/Alarm Functions

Conditions or events in the APD system may trigger alerts and/or alarmsthat are logged, displayed to a user, or both. These alerts and alarmsare a user interface construct that reside in the user interfacesubsystem, and may be triggered by conditions that occur in any part ofthe system. These conditions may be grouped into three categories: (1)system error conditions, (2) therapy conditions, and (3) systemoperation conditions.

“System error conditions” relate to errors detected in software, memory,or other aspects of the processors of the APD system. These errors callthe reliability of the system into question, and may be considered“unrecoverable.” System error conditions cause an alarm that isdisplayed or otherwise made known to the user. The alarm may also belogged. Since system integrity cannot be guaranteed in the instance of asystem error condition, the system may enter a fail safe mode in whichthe safe line described herein is disabled.

Each subsystem described in connection with FIG. 130 is responsible fordetecting its own set of system errors. System errors between subsystemsare monitored by the user interface computer executive 352 andautomation computer executives 354. When a system error originates froma process running on the user interface computer 302, the processreporting the system error terminates. If the UI screen view subsystem338 is terminated, the user interface computer executive 352 attempts torestart it, e.g., up to a maximum of three times. If it fails to restartthe UI screen view 338 and a therapy is in progress, the user interfacecomputer executive 352 transitions the machine to a fail safe mode.

When a system error originates from a process running on the automationcomputer 300, the process terminates. The automation computer executive354 detects that the process has terminated and transitions to a safestate if a therapy is in progress.

When a system error is reported, an attempt is made to inform the user,e.g., with visual and/or audio feedback, as well as to log the error toa database. System error handling is encapsulated in the executivesubsystem 332 to assure uniform handling of unrecoverable events. Theexecutive processes of the UIC executive 352 and AC executive 354monitor each other such that if one executive process fails duringtherapy, the other executive transitions the machine to a safe state.

“Therapy conditions” are caused by a status or variable associated withthe therapy going outside of allowable bounds. For example, a therapycondition may be caused by an out-of-bounds sensor reading. Theseconditions may be associated with an alert or an alarm, and then logged.Alarms are critical events, generally requiring immediate action. Alarmsmay be prioritized, for example as low, medium or high, based on theseverity of the condition. Alerts are less critical than alarms, andgenerally do not have any associated risk other than loss of therapy ordiscomfort. Alerts may fall into one of three categories: messagealerts, escalating alerts, and user alerts.

The responsibility for detecting therapy conditions that may cause analarm or alert condition is shared between the UI model and therapysubsystems. The UI model subsystem 360 (FIG. 158) is responsible fordetecting alarm and alert conditions pre-therapy and post-therapy. Thetherapy subsystem 340 (FIG. 130) is responsible for detecting alarm andalert conditions during therapy.

The responsibility for handling alerts or alarms associated with therapyconditions is also shared between the UI model and therapy subsystems.Pre-therapy and post-therapy, the UI model subsystem 360 is responsiblefor handling the alarm or alert condition. During a therapy session, thetherapy subsystem 340 is responsible for handling the alarm or alertcondition and notifying the UI Model Subsystem an alarm or alertcondition exists. The UI model subsystem 360 is responsible forescalating alerts, and for coordinating with the UI view subsystem 338to provide the user with visual and/or audio feedback when an alarm oralert condition is detected.

“System operation conditions” do not have an alert or alarm associatedwith them. These conditions are simply logged to provide a record ofsystem operations. Auditory or visual feedback need not be provided.

Actions that may be taken in response to the system error conditions,therapy conditions, or system operation conditions described above areimplemented by the subsystem (or layer) that detected the condition,which sends the status up to the higher subsystems. The subsystem thatdetected the condition may log the condition and take care of any safetyconsiderations associated with the condition. These safetyconsiderations may comprise any one or combination of the following:pausing the therapy and engaging the occluder; clearing states andtimers as needed; disabling the heater; ending the therapy entirely;deactivating the safe line to close the occluder, shut off the heater,and removing power from the valves; and preventing the cycler fromrunning therapies even after a power cycle to require the system to besent back to service. The UI subsystem 334 may be responsible forconditions that can be cleared automatically (i.e., non-latchingconditions) and for user recoverable conditions that are latched and canonly be cleared by user interaction.

Each condition may be defined such that it contains certain informationto allow the software to act according to the severity of the condition.This information may comprise a numeric identifier, which may be used incombination with a lookup table to define priority; a descriptive nameof the error (i.e., a condition name); the subsystem that detected thecondition; a description of what status or error triggers the condition;and flags for whether the condition implements one or more actionsdefined above.

Conditions may be ranked in priority such that when multiple conditionsoccur, the higher priority condition may be handled first. This priorityranking may be based on whether the condition stops the administrationof therapy. When a condition occurs that stops therapy, this conditiontakes precedence when relaying status to the next higher subsystem. Asdiscussed above, the subsystem that detects a condition handles thecondition and sends status information up to the subsystem above. Basedon the received status information, the upper subsystem may trigger adifferent condition that may have different actions and a differentalert/alarm associated with it. Each subsystem implements any additionalactions associated with the new condition and passes status informationup to the subsystem above. According to one exemplary implementation,the UI subsystem only displays one alert/alarm at a given time. In thiscase, the UI model sorts all active events by their priority anddisplays the alert/alarm that is associated with the highest priorityevent.

A priority may be assigned to an alarm based on the severity thepotential harm and the onset of that harm. Table 1, below, shows anexample of how priorities may be assigned in this manner.

TABLE 1 POTENTIAL RESULT OF FAILURE TO RESPOND TO THE CAUSE OF ALARMONSET OF POTENTIAL HARM CONDITION IMMEDIATE PROMPT DELAYED death orirreversible high priority high priority medium priority injuryreversible injury high priority medium low priority priority minordiscomfort or medium priority low priority low priority or no injuryalarm signal

In the context of Table 1, the onset of potential harm refers to when aninjury occurs and not to when it is manifested. A potential harm havingan onset designated as “immediate” denotes a harm having the potentialto develop within a period of time not usually sufficient for manualcorrective action. A potential harm having an onset designated as“prompt” denotes a harm having the potential to develop within a periodof time usually sufficient for manual corrective action. A potentialharm having an onset designated as “delayed” denotes a harm having thepotential to develop within an unspecified time greater than that givenunder “prompt.”

FIGS. 161-166 show exemplary screen views relating to alerts and alarmsthat may be displayed on a touch screen user interface. FIG. 161 showsthe first screen of an alarm, which includes a diagram 380 and text 382instructing a user to close their transfer set. The screen includes avisual warning 384, and is also associated with an audio warning. Theaudio warning may be turned off my selecting the “audio off” option 386on the touch screen. When the user has closed the transfer set, the userselects the “confirm” option 388 on the touch screen. FIG. 162 shows asimilar alarm screen instructing a user to close their transfer set. Inthis case, an indication that draining is paused 390 and an instructionto select “end treatment” are provided 392.

As previously discussed, alerts generally do not have associated riskother than loss of therapy or discomfort. Thus, an alert may or may notcause the therapy to pause. Alerts can be either “auto recoverable,”such that if the event clears the alert automatically clears, or “userrecoverable,” such that user interaction with the user interface isneeded to clear the alert. An audible alert prompt, which may have avolume that may be varied within certain limits, may be used to bring analert to the attention of a user. In addition, information or aninstruction may be displayed to the user. So that such information orinstruction may be viewed by the user, an auto-dim feature of the userinterface may be disabled during alerts.

In order to reduce the amount of disturbance to the user, alerts may becategorized into different types based on how important an alert is andhow quick a user response is required. Three exemplary types of alertsare a “message alert,” an “escalating alert,” and a “user alert.” Thesealerts have different characteristics based on how information isvisually presented to the user and how the audible prompt is used.

A “message alert” may appear at the top of a status screen and is usedfor informational purposes when a user interaction is not required.Because no action needs to be taken to clear the alert, an audibleprompt is generally not used to avoid disturbing, and possibly waking,the patient. However, an audible alert may be optionally presented. FIG.163 shows an exemplary message alert. In particular, FIG. 163 shows anunder-temperature message alert 394 that may be used to inform a userwhen the dialysate is below a desired temperature or range. In thiscase, a user does not need to take any action, but is informed thattherapy will be delayed while the dialysate is heated. If the patientdesires more information, the “view” option 396 may be selected on thetouch screen. This causes additional information 398 concerning thealert to appear on the screen, as shown in FIG. 164. A message alert mayalso be used when there is a low flow event that the user is trying tocorrect. In this case, a message alert may be displayed until the lowflow event is cleared to provide feedback to the user on whether theuser fixed the problem.

An “escalating alert” is intended to prompt the user to take action in anon-jarring manner. During an escalating alert, a visual prompt maydisplayed on the touch screen and an audible prompt may be presented(e.g., once). After a given period of time, if the event that caused thealert is not cleared, a more emphatic audible prompt may be presented.If the event causing the alert is not cleared after an additional periodof time, the alert is escalated to a “user alert.” According to oneexemplary implementation of a user alert, a visual prompt is displayeduntil the alert is cleared and an audible prompt, which can be silenced,is presented. The UI subsystem does not handle the transition to fromescalating alert to user alert. Rather, the subsystem that triggered theoriginal event will trigger a new event associated with the user alert.FIG. 165 shows a screen view displaying information concerning anescalating alert. This exemplary alert includes an on-screen alertmessage 400 and a prompt 402 instructing the user to check the drainline for kinks and closed clamps, as well as and an audible prompt. Theaudible prompt may be continuous until it is silenced by the user. FIG.166 shows a screen view including an “audio off” option 404 that may beselected to silence the audible prompt. This alert can be used directly,or as part of the escalating alert scheme.

Each alert/alarm is specified by: an alert/alarm code, which is a uniqueidentifier for the alert/alarm; an alert/alarm name, which is adescriptive name of the alert/alarm; an alert/alarm type, whichcomprises the type of alert or level of alarm; an indication of whetheran audible prompt is associated with the alert/alarm; an indication ofwhether the alert and associated event can be bypassed (or ignored) bythe user; and the event code of the event or events that trigger thealert/alarm.

During alarms, escalating alerts and user alerts, the event code (whichmay be different from the alert or alarm code, as described above) maybe displayed on the screen so that the user can read the code to servicepersonnel if needed. Alternatively or additionally, a voice guidancesystem may be used so that, once connected to a remote call center, thesystem can vocalize pertinent information about the systemconfiguration, state, and error code. The system may be connected to theremote call center via a network, telephonic connection, or some othermeans.

An example of a condition detected by the therapy subsystem is describedbelow in connection with FIG. 167. The condition results when the APDsystem is not positioned on a level surface, which is important for airmanagement. More particularly, the condition results when a tilt sensordetects that APD system is tilted beyond a predetermined threshold, suchas 35°, with respect to a horizontal plane. As described below, arecoverable user alert may be generated by the therapy subsystem if thetilt sensor senses an angle with an absolute value greater than thepredetermined threshold. To avoid nuisance alarms, the user may bedirected to level the APD system before therapy begins. The tiltthreshold may be lower during this pre-therapy period (e.g., 35°). Theuser may also be given feedback concerning whether the problem iscorrected.

When the tilt sensor detects an angle of tilt exceeding a thresholdvalue during therapy, the machine subsystem 342 responds by stopping thepump in a manner similar to detecting air in the pump chamber. Thetherapy subsystem 340 asks for status and determines that the machinelayer 342 has paused pumping due to tilt. It also receives statusinformation concerning the angle of the machine. At this point, thetherapy subsystem 340 generates a tilt condition, pauses therapy, andsends a command to the machine subsystem 342 to pause pumping. Thiscommand triggers clean-up, such as taking fluid measurement system (FMS)measurements and closing the patient valve. The therapy subsystem 340also starts a timer and sends an auto recoverable tilt condition up tothe UI model 360, which sends the condition to the UI view 338. The UIview 338 maps the condition to an escalating alert. The therapysubsystem 340 continues to monitor the tilt sensor reading and, if itdrops below the threshold, clears the condition and restarts therapy. Ifthe condition does not clear before the timer expires, the therapysubsystem 340 triggers a user recoverable “tilt timeout” condition thatsupersedes the auto-recoverable tilt condition. It sends this conditionto the UI model 360, which sends the condition to the UI view 338. TheUI view 338 maps the condition to a user alert. This condition cannot becleared until a restart therapy command is received from the UIsubsystem (e.g., the user pressing the resume button). If the tiltsensor reading is below the threshold, the therapy resumes. If it is notbelow the threshold, the therapy layer triggers an auto recoverable tiltcondition and starts the timer.

Prioritized Audible Signals

The cycler may provide audible signals and voice guidance to the user tocommunicate a range of information including but not limited to numberselection, sound effects (button selection, action selection), machinecondition, operational directions, alerts, and alarms. The cyclercontroller 16 may cause a speaker to annunciate audible signals andvocalizations from stored sound files stored in memory on one or both ofthe computers 300, 302 in the control system 16. Alternatively,vocalizations may be stored and produced by a specialized voice chip.

In some instances, the cycler may have multiple audible signals toannunciate at the same time or sequentially in a very short time. Theannunciation of several signals in a short period of time may overwhelmthe user resulting in annoyance or the loss of critical safetyinformation. The cycler controller 16 may assign priorities to eachaudible signal and suppress the lower priority signals to allow theclear communication of higher priority audible signals. In one instance,the audible signals are prioritized from the highest priority alarmsignals to the lowest priority annunciation of a sequence of numbers:

1. Alarms

2. Alerts

3. Sound Effects

4. Voice Guidance

5. Annunciation for a sequence of numbers.

Alarms and alerts are described above. Sound effects may confirm soundsto indicate that a button, or choice has been selected. Sound effectsmay also announce or confirm a particular action is being taken by thecycler. Voice guidance may include voiced instructions to execute aparticular procedure, access help, contact a call center and otherdirecting instructions. Annunciation for a sequence of numbers mayinclude reading back to the user or the call center the number that theuser had just keyed in or it may read the user allowable values forrequested input.Audible Sleep Aid

The cycler 14 may include an option to play soothing sounds at night toaid sleeping. The playing of sounds such as rain, ocean waves, etc. arereferred to as sound therapy. Sound therapy for sleep can provide someusers with a higher tolerance for nighttime noises and the masking orreplacing of nighttime noise with more rhythmic, soothing sounds thatminimize sleep disturbance. Sound therapy may help individuals sufferingfrom hearing conditions such as hyperacusis and tinnitus. The userinterface 324 may provide the user with a menu to select types of sound,volume levels and duration so that the sound therapy can play beforeand/or during the initial period of sleep. The sound files may be storedin the memories of the computers 300, 302 and played by the speaker inthe cycler 14. In another example, the cycler may include an output jackto drive external speakers. In another example, the sound files and/orthe speaker driver electronics may be separate from either theautomation computer 300 or the user interface computer 302. The soundfiles may include the but be limited to rain sounds, thunder storms,ocean waves, thunder, forest sounds, crickets, white noise, and pinknoise (varying amplitude and more bass).

Battery Operation

The cycler may include a rechargeable lithium ion battery for use as abackup power source. At a minimum this battery helps to ensure that thecycler does not turn off without alerting the user and saving thecurrent state of the treatment. A power management system may beimplemented by the cycler when on battery power that is contingent onthe amount of charge remaining in the battery. If the battery issufficiently charged, the cycler can prevent brownouts or short poweroutages from interfering with the completion of a therapy. The cyclercontrol circuitry can measure the state of charge of the battery, andcan correlate the battery charge level with operable states. Thisinformation may be obtained empirically through testing, and thecorrelations between battery charge level and the ability to operate thevarious subsystems may be stored in memory. The following functions maybe associated with the battery charge level:

-   Level 4: Enough power to perform one cycle of therapy. Implemented    if, for example, the charge level of the battery is equal to or    greater than approximately 1100 milliamp-hours.-   Level 3: Enough power to perform a user drain. Implemented if, for    example, the charge level of the battery is equal to or greater than    approximately 500 milliamp-hours.-   Level 2: Enough power to end therapy, display alert, and guide user    through post-therapy breakdown. Implemented if, for example, the    charge level of the battery is equal to or greater than    approximately 300 milliamp-hours.-   Level 1: Enough power to end therapy and display an alert.    Implemented if, for example, the charge level of the battery is    equal to or greater than approximately 200 milliamp-hours.-   Level 0: Not enough power to operate.

If there is enough charge in the battery (Level 4), the cycler willcontinue with the therapy until the current cycle is finished. This maynot include replenishing the heater bag or heating the solution.Therefore, if already in a fill phase, the cycler may continue thetherapy if the solution in the heater bag is in the proper temperaturerange and there is enough solution in the heater bag. If the batteryonly has enough capacity to perform a 20 minute drain (Level 3), thecycler will alert the user, and give the user the option to either drainor end treatment without draining. If the battery only has enough powerto alert the user (Level 2) it will not give the user the option todrain and the user will be guided through the post-therapy breakdown. Ifthere is not enough power to guide the user through breakdown (Level 1),the user will be prompted to disconnect and then the cycler will powerdown. At this battery level the cycler may not have enough power torelease the door, so the user may not be able to breakdown the therapy.During start up, the cycler can assess the state of the batter, andalert the user if the battery has a fault or if the battery does nothave a sufficient charge to at least alert the patient if main power islost. The cycler may be programmed to not allow the user to start atreatment without the battery having enough capacity to provide andalert and guide the user through post-therapy breakdown (Battery Level2).

Another example of battery charge levels and available therapy choicesor machine actions sets 4 battery charge levels and the availabletherapy choices or machine actions:

Level 4:

If the fill process has not started, then suspend operation until the ACpower is restored. The suspend is limited to 30 mins.

If the fill process has started, then complete cycle including the fill,dwell and drain processes.

The heater bag will not be refilled as there is no heating duringbattery operation.

End therapy, and guide user through post-therapy breakdown includingremoval of the of the dialysate delivery set 12 a from the cycler 14.

Level 3:

If in the fill or drain process, then suspend operation until the ACpower is restored. The suspend is limited to 30 mins.

If the drain process has started, then complete the cycle.

The heater bag will not be refilled as there is no heating duringbattery operation.

End therapy, and guide user through post-therapy breakdown includingremoval of the of the dialysate delivery set 12 a from the cycler 14.

Level 2:

End therapy, and guide user through post-therapy breakdown includingremoval of the of the dialysate delivery set 12 a from the cycler 14.

Level 1:

End therapy.

Level 0:

Not enough power to operate.

An alert will be displayed to the user or patient at levels 1-4. Thecontrol system 16 may extend the cycler operation on battery power bydimming the display screen 324 after a given time period from the lastscreen touch. In another example the display screen 324 may dim after agiven period from the appearance of the most recent message, alert orwarning. In one example, the display screen 324 will dim 2 minutes afterthe more recent screen touch or last. The display screen 324 may includea message or symbol indicating operation on battery power.

The electrical circuitry connecting the battery to the pneumatic valvesmay include a regulated voltage boost converter that steps-up thesupplied variable battery voltage to a consistent voltage. The suppliedbattery voltage may drop as the battery is discharged, in one example, aLi-Ion battery at full charge may supply 12.3 volts. The suppliedvoltage may drop as the battery is depleted to as low as 9 volts whenthe battery is fully discharged. The pneumatic valves may require aminimum voltage to reliably open fully. In one example, the minimumvoltage to reliably open the valve may be 12 volts.

A regulated voltage boost converter may be placed between the supplybattery and the valves to assure sufficient voltage to reliably open thevalves as battery discharges. The regulated voltage boost converter willoutput a regulated voltage at a higher value than the variable batteryvoltage input. In one example, the regulated voltage boost converter maybe an integrated chip such as the TPS61175 made by Texas Instruments. Aregulated voltage buck/boost converter may also be used between thebattery and the valves. The buck/boost converter is able to supply aregulated voltage output from supplied voltages that are higher, equalto, or lower than the input voltage.

In one embodiment, the PWM duty cycle of the valve drivers may vary withthe measured battery voltage. The valves may be operated in apick-and-hold manner, where an initially higher voltage is applied toopen the valve and then a lower voltage is applied to hold the valve indesired condition. The PWM duty cycle for the hold function may bescaled inversely with the measure battery voltage to provide aconsistent averaged voltage or current to the valves. The PWM duty cyclemay be scaled inversely with measured battery voltage for the highervoltage open or pick operation.

Screen Display

As discussed previously, the UI view subsystem 338 (FIG. 158) isresponsible for the presentation of the interface to the user. The UIview subsystem is a client of and interfaces with the UI model subsystem360 (FIG. 158) running on the automation computer. For example, the UIview subsystem communicates with the UI model subsystem to determinewhich screen should be displayed to the user at a given time. The UIview may include templates for the screen views, and may handlelocale-specific settings such as display language, skin, audio language,and culturally sensitive animations.

There are three basic types of events that occur in the UI viewsubsystem. These are local screen events that are handled by theindividual screens, model events in which a screen event must propagatedown to the UI model subsystem, and polling events that occur on a timerand query the UI model subsystem for status. A local screen event onlyaffects the UI view level. These events can be local screen transitions(e.g., in the case of multiple screens for a single model state),updates to view settings (e.g., locality and language options), andrequests to play media clips from a given screen (e.g., instructionalanimations or voice prompts). Model events occur when the UI viewsubsystem must consult with the UI model subsystem to determine how tohandle the event. Examples that fall into this category are theconfirmation of therapy parameters or the pressing of the “starttherapy” button. These events are initiated by the UI view subsystem,but are handled in the UI model subsystem. The UI model subsystemprocesses the event and returns a result to the UI view subsystem. Thisresult drives the internal state of the UI view subsystem. Pollingevents occur when a timer generates a timing signal and the UI modelsubsystem is polled. In the case of a polling event, the current stateof the UI view subsystem is sent to the UI model subsystem forevaluation. The UI model subsystem evaluates the state information andreplies with the desired state of the UI view subsystem. This mayconstitute: (1) a state change, e.g., if the major states of the UImodel subsystem and the UI view subsystem are different, (2) a screenupdate, e.g., if values from the UI model subsystem change valuesdisplayed on-screen, or (3) no change in state, e.g., if the state ofthe UI model subsystem and the UI view subsystem are identical. FIG. 168shows the exemplary modules of the UI view subsystem 338 that performthe functions described above.

As shown in FIG. 168, the UI model client module 406 is used tocommunicate events to the UI model. This module 406 is also used to pollthe UI model for the current status. Within a responsive status message,the UI model subsystem may embed a time to be used to synchronize theclocks of the automation computer and the user interface computer.

The global slots module 408 provides a mechanism by which multiplecallback routines (slots) can subscribe to be notified when given events(signals) occur. This is a “many-to-many” relationship, as a slot can bebound to many signals, and likewise a signal can be bound to many slotsto be called upon its activation. The global slots module 408 handlesnon-screen specific slots, such as application level timers for UI modelpolling or button presses that occur outside of the screen (e.g., thevoice prompt button).

The screen list class 410 contains a listing of all screens in the formof templates and data tables. A screen is made up of a template and anassociated data table that will be used to populate that screen. Thetemplate is a window with widgets laid out on it in a generic manner andwith no content assigned to the widgets. The data table includes recordsthat describe the content used to populate the widgets and the state ofthe widgets. A widget state can be checked or unchecked (in the case ofa checkbox style widget), visible or hidden, or enabled or disabled. Thedata table can also describe the action that occurs as a result of abutton press. For example, a button on window ‘A’ derived from template‘1’ could send an event down to the UI model, whereas that same buttonon window ‘B’ also derived from template ‘1’ could simply cause a localscreen transition without propagating the event down to the UI model.The data tables may also contain an index into the context-sensitivehelp system.

The screen list class 410 forwards data from the UI model to theintended screen, selects the proper screen-based data from the UI model,and displays the screen. The screen list class 410 selects which screento display based on two factors: the state reported by the UI model andthe internal state of the UI view. In some cases, the UI model may onlyinform the UI view that it is allowed to display any screen within acategory. For example, the model may report that the machine is idle(e.g., no therapy has been started or the setup phase has not yetoccurred). In this case, it is not necessary to confer with the UI modelwhen the user progresses from a menu into its sub-menu. To track thechange, the UI view will store the current screen locally. This localsequencing of screens is handled by the table entries described above.The table entry lists the actions that respective buttons will initiatewhen pressed.

The language manager class 412 is responsible for performing inventoryon and managing translations. A checksum may be performed on the list ofinstalled languages to alert the UI view if any of the translations arecorrupted and or missing. Any class that wants a string translated asksthe language manager class 412 to perform it. Translations may behandled by a library (e.g., Qt®). Preferably, translations are requestedas close as possible to the time of rendering. To this end, most screentemplate member access methods request a translation right beforehanding it to the widget for rendering.

A skin comprises a style-sheet and images that determine the “look andfeel” of the user interface. The style-sheet controls things such asfonts, colors, and which images a widget will use to display its variousstates (normal, pressed, disabled, etc.). Any displayed widget can haveits appearance altered by a skin change. The skin manager module 414 isresponsible for informing the screen list and, by extension, the screenwidgets, which style-sheet and skin graphics should be displayed. Theskin manager module 414 also includes any animated files the applicationmay want to display. On a skin change event, the skin manager willupdate the images and style-sheet in the working set directory with theproper set, which is retrieved from an archive.

The video manager module 416 is responsible for playinglocale-appropriate video given a request to display a particular video.On a locale change event, the video manager will update the videos andanimations in the working set directory with the proper set from anarchive. The video manager will also play videos that have accompanyingaudio in the audio manager module 418. Upon playback of these videos,the video manager module 416 will make the appropriate request to theaudio manager module 418 to play the recording that belongs to theoriginally requested video clip.

Similarly, the audio manager module 418 is responsible for playinglocale-appropriate audio given a request to play a particular audioclip. On a locale change event, the audio manager will update the audioclips in the working set directory with the proper set from an archive.The audio manager module 418 handles all audio initiated by the UI view.This includes dubbing for animations and sound clips for voice prompts.

The database client module 420 is used to communicate with the databasemanager process, which handles the interface between the UI viewsubsystem and the database server 366 (FIG. 158). The UI view uses thisinterface to store and retrieve settings, and to supplement therapy logswith user-provided answers to questions about variables (e.g., weightand blood pressure).

The help manager module 422 is used to manage the context-sensitive helpsystem. Each page in a screen list that presents a help button mayinclude an index into the context-sensitive help system. This index isused so that the help manager can display the help screen associatedwith a page. The help screen may include text, pictures, audio, andvideo.

The auto ID manager 424 is called upon during pre-therapy setup. Thismodule is responsible for capturing an image (e.g., a photographicimage) of a solution bag code (e.g., a datamatrix code). The dataextracted from the image is then sent to the machine control subsystemto be used by the therapy subsystem to identify the contents of asolution bag, along with any other information (e.g., origin) includedin the code.

Using the modules described above, the UI view subsystem 338 renders thescreen views that are displayed to the user via the user interface(e.g., display 324 of FIG. 127). FIGS. 169-175 show exemplary screenviews that may be rendered by the UI view subsystem. These screen viewsillustrate, for example, exemplary input mechanisms, display formats,screen transitions, icons and layouts. Although the screens shown aregenerally displayed during or before therapy, aspects of the screenviews may be used for different input and output functions than thoseshown.

The screen shown in FIG. 169 is an initial screen that provides the userthe option of selecting between “start therapy” 426 to initiate thespecified therapy 428 or “settings” 430 to change settings. Icons 432and 434 are respectively provided to adjust brightness and audio levels,and an information icon 436 is provided to allow the user to solicitmore information. These icons may appear on other screens in a similarmanner.

FIG. 170 shows a status screen that provides information the status ofthe therapy. In particular, the screen indicates the type of therapybeing performed 438, the estimated completion time 440, and the currentfill cycle number and total number of fill cycles 442. The completionpercentage of the current fill cycle 444 and the completion percentageof the total therapy 446 are both numerically and graphically displayed.The user may select a “pause” option 448 to pause therapy.

FIG. 171 shows a menu screen with various comfort settings. The menuincludes brightness arrows 450, volume arrows 452 and temperature arrows454. By selecting either the up or down arrow in each respective pair, auser can increase or decrease screen brightness, audio volume, and fluidtemperature. The current brightness percentage, volume percentage andtemperature are also displayed. When the settings are as desired, a usermay select the “OK” button 456.

FIG. 172 shows a help menu, which may be reached, for example, bypressing a help or information button on a prior screen. The help menumay include text 458 and/or an illustration 460 to assist the user. Thetext and/or illustration may be “context sensitive,” or based on thecontext of the prior screen. If the information provided to the usercannot conveniently be provided in one screen, for example in the caseof a multi-step process, arrows 462 may be provided to allow the user tonavigate backward and forward between a series of screens. When the userhas obtained the desired information, he or she may select the “back”button 464. If additional assistance is required, a user may select the“call service center” option 466 to have the system contact the callservice center.

FIG. 173 illustrates a screen that allows a user to set a set ofparameters. For example, the screen displays the current therapy mode468 and minimum drain volume 470, and allows a user to select theseparameters to be changed. Parameters may be changed in a number of ways,such as by selecting a desired option from a round robin style menu onthe current screen. Alternatively, when the user selects a parameter tobe changed, a new screen may appear, such as that shown in FIG. 174. Thescreen of FIG. 174 allows a user to adjust the minimum drain volume byinputting a numeric value 472 using a keypad 474. Once entered, the usermay confirm or cancel the value using buttons 476 and 478. Referringagain to FIG. 173, a user may then use the “back” and “next” arrows 480,482 to navigate through a series of parameters screens, each including adifferent set of parameters.

Once all desired parameters have been set or changed (e.g., when theuser has navigated through the series of parameters screens), a screensuch as that shown in FIG. 175 may be presented to allow a user toreview and confirm the settings. Parameters that have changed mayoptionally be highlighted in some fashion to draw the attention of theuser. When the settings are as desired, a user may select the “confirm”button 486.

Automated Peritoneal Dialysis Therapy Control

Continuous ambulatory peritoneal dialysis (“CAPD”) is traditionallyperformed manually, with a patient or user transferring dialysissolution from a bag into his or her peritoneal cavity, having the fluiddwell in the abdomen for three to six hours, and then allowing the fluidto empty into a collection or drain bag. This is typically done three orfour times a day. Automated peritoneal dialysis (“APD”) differs fromCAPD in that APD is achieved with the aid of a peritoneal dialysismachine (“cycler”) that performs a series of fill-dwell-drain cyclesduring a period of several hours (e.g. when asleep or at night). In APD,the fluid introduced during a fill phase of a cycle, plus anyultrafiltration fluid, may not drain completely during the followingdrain phase of the cycle. This may be a result of the user's position inbed, leading to sequestration of fluid, for example, in a recess in theperitoneal cavity, and preventing an indwelling catheter from accessingall of the fluid present. In continuous cycling peritoneal dialysis(“CCPD”), the cycler attempts to perform a full drain after a fill anddwell phase in order to prevent accumulation of retained fluid (aresidual intraperitoneal volume) with each succeeding cycle. APDgenerally comprises a plurality of short nighttime exchanges ofdialysate while the user is connected to the cycler and asleep. At theend of a nighttime therapy, a volume of dialysis fluid—possibly ofdifferent composition—may be left in the peritoneal cavity during theday for continued exchange of solutes, transfer of waste compounds, andultrafiltration. In intermittent peritoneal dialysis (“IPD”), multipleexchanges of dialysate are performed over a period of time (e.g., atnight), without having a prolonged residual (or daytime) dwell cycle.

Therapy with a cycler generally begins with an initial drain phase toattempt to ensure that the peritoneal cavity is empty of fluid. Thecharacteristics of the dialysate solution usually cause some transfer offluid from the patient's tissues to the intraperitonealspace—ultrafiltration. As therapy proceeds through a series of cycles,fluid may accumulate in the intraperitoneal cavity if the drain phasedoes not yield the volume of fluid infused during the fill phase, plusthe volume of ultrafiltered fluid produced during the time thatdialysate solution is in the peritoneal cavity. In some modes, thecycler may be programmed to issue an alarm to the user when the drainvolume has not matched the volume of fluid infused plus the expectedultrafiltration (“UF”) volume. The expected UF volume is a functionof—among other things—the individual patient's physiology, the chemicalcomposition of the dialysate solution, and the time during which thedialysate solution is expected to be present in the peritoneal cavity.

In other modes, the cycler may proceed to the next fill-dwell-draincycle if a pre-determined amount of drain time has passed and apre-determined minimum percentage (e.g. 85%) of the preceding fillvolume has been drained. In this case, the cycler may be programmed toalarm if the drain flow decreases below a pre-determined rate after theminimum drain time and before the minimum drain percentage has beenreached. The cycler may be programmed to alert the user after severalminutes (e.g., two minutes) of attempting but failing to maintain apre-determined flow rate when pumping fluid from the peritoneal cavity.A low-flow condition may be detectable by the cycler because of theincreased amount of time required to fill a pump chamber beforeend-of-stroke is detected by the controller. A zero-flow or no-flowcondition may be detectable by the cycler because of the detection bythe controller of a premature end-of-stroke state. The duration of thetime delay before alerting the user or initiating a new fill-dwell-draincycle may be programmed to be a few minutes in a low-flow condition(e.g., 2 minutes), and may be shorter (e.g., 30 seconds) in a no-flowcondition. A shorter wait-time during a no-flow condition may bepreferable, for example, because it may be associated with a greaterdegree of patient discomfort, or may be the result of a quicklycorrectable problem, such as a bend in the patient line or catheter.This time delay may be programmed at the cycler manufacturing stage ormay be selectable by a clinician as a prescription parameter. The extentof the delay may be governed, among other things, by the countervailingdesire of the user or clinician to stay within the targeted totaltherapy time (keeping in mind that little dialysis is likely to occurwhen the intraperitoneal volume (“IPV”) is low or close to zero). If afull drain is not achieved, the cycler may also track the amount offluid estimated to be accumulating with each cycle, and issue a warningor alarm if the cumulative IPV exceeds a pre-determined amount. Thismaximum IPV may be a parameter of the therapy prescription programmedinto the cycler by the clinician, taking account of the particularphysiological characteristics of the individual patient/user.

One method of dealing with the cumulative retention of fluid during aseries of CCPD cycles is to convert the CCPD therapy to a tidalperitoneal dialysis (“TPD”) therapy. TPD generally comprises afill-dwell-drain cycle in which a drain volume is intentionally made aprescribed fraction of the initial fill volume (which may also beinitially be entered by the clinician as a prescription parameter). Apre-determined percentage of the infused fluid, or a pre-determinedamount of fluid is arranged to remain in the peritoneal cavity duringthe subsequent fill-dwell-drain cycles during a therapy. Preferably, thesubsequent fill volumes are also reduced to match the drain volume(minus the expected UF) in order to maintain a relatively constantresidual intraperitoneal volume. For example, an initial fill volume of3000 ml may be introduced at the beginning of therapy, followed bysubsequent drain and fill plus expected UF volumes amounting to only1500 ml, i.e. 50% of the initial fill volume. The reserve or residualfluid in the peritoneal cavity is then drained completely at the end oftherapy. In an alternative mode, a complete drain may be attempted aftera pre-determined or prescribed number of fill-dwell-drain cycles (e.g.,a complete drain may be attempted after three cycles of tidal therapy,this grouping comprising a therapy “cluster”). TPD may be beneficial inthat users may experience less discomfort associated with repeated largefill volumes or repeated attempts to fully empty the peritoneal cavity.Low-flow conditions associated with small intraperitoneal fluid volumesmay also be reduced, thus helping to avoid extending the total therapytime. To reduce the discomfort associated with attempting to drain smallresidual volumes, for example, the tidal drain volume may be set at 75%of the initial fill volume (plus-or-minus expected UF volume), forexample, leaving approximately 25% as a reserve or residual volume inthe peritoneal cavity for the duration of therapy, or for the durationof a cluster of cycles.

A cycler may also be programmed to convert a CCPD mode of therapy to aTPD mode of therapy during the course of therapy if the user chooses tokeep a residual volume of fluid in the peritoneal cavity at the end ofthe subsequent drain phases (e.g., for comfort reasons). In this case,the cycler is programmed to calculate a choice of residual volumes (orvolumes as a percent of initial fill volume) based on the number ofextra cycles to be added to the therapy and the volume of remainingdialysate to be infused. For example, the cycler controller cancalculate the remaining fill volumes based on the remaining cycles thatinclude an additional one, two or more cycles. Having determined thefill volumes for each of these possibilities, the cycler controller cancalculate how much residual volume can be left at the end of eachremaining drain phase while ensuring that the IPV remains under amaximum prescribed IPV (Max IPV). The cycler may then present the userwith a range of possible residual volumes (as a percentage of theinitial fill volume or in volumetric terms) available for each remainingcycle in a therapy extended by one, two or more cycles. The user maymake the selection based on the number of extra cycles chosen and thedesired amount of post-drain residual volume. Switching to tidal therapymay help to reduce the number of low-drain-flow alerts to the user,which can be particularly advantageous during nighttime therapy.

In switching to tidal mode, the cycler may be programmed to select areserve or residual volume percentage (volume remaining in theperitoneal cavity as a percent of the fill volume plus expected UF).Alternatively, the reserve volume may be user-selectable orclinician-selectable from a range of values, optionally with theclinician having the ability to select a wider range of possible valuesthan the user. In an embodiment, the cycler may calculate the effects ofadding one, two or three additional cycles on the remaining fill volumesand the expected residual IP volume percentage, and give the user orclinician the option of selecting among those calculated values.Optionally, the cycler may be constrained to keep the residual IP volumepercentage below a pre-determined maximum value (e.g., a percentage ofthe initial fill volume plus expected UF, or a percentage of the maximumpermissible IPV).

If CCPD is converted to TPD, one or more therapy cycles(fill-dwell-drain cycles) may need to be added to a therapy to use allof the prescribed volume of dialysate for the therapy session. Theremaining volume to be infused going forward would then be divided bythe remaining number of cycles. Furthermore, the cycler may beprogrammed to allow the clinician or user to select between extendingthe targeted total therapy time to accommodate the additional cycles(cycle-based therapy), or to attempt to maintain the targeted therapytime by adjusting the dwell times (i.e., shortening them) if necessaryto reduce the fill-dwell-drain cycle durations going forward (time-basedtherapy).

In an alternative embodiment, the cycler may allow the residual IPvolume to fluctuate (optionally within pre-determined limits) from onecycle to the next, depending on how much fluid can be drained within aspecified drain time interval. The time available for the drain phasemay be limited if the cycler has been programmed to complete the therapywithin the previously scheduled time, or the drain phase may beterminated to prevent the cycler from attempting to pull fluid at a slowrate for a prolonged period of time. In switching from CCPD to TPD, ifthe cycler adds one or more additional cycles to perform a completetherapy with the available dialysate solution, then meeting thescheduled therapy end-time may require shortening the dwell times, orreducing each drain phase, which could cause the residual volume for thetidal mode to vary, depending on the drain flow conditions. As thecycler estimates and tracks the amount of residual volume, it may beprogrammed to calculate whether the subsequent fill volume plus expectedUF volume will reach or exceed a prescribed maximum IPV. If so, thecycler can alert and provide the user with two or more options: the usermay terminate treatment, repeat or extend a drain phase in an attempt tolower the residual intraperitoneal volume, or add a cycle to reduce thesubsequent fill volumes. After calculating the effect on treatment timeof adding an additional one or more cycles (increased number of cyclesvs. reduced fill and drain times at lower volumes) the cycler mayoptionally reduce subsequent dwell times by an amount of time necessaryto offset the additional therapy time generated by an additional one ormore cycles.

The cycler may be programmed to deliver an optional last-fill phase thatdelivers fresh dialysate of the same or a different composition to theuser's peritoneal cavity for an extended dwell time while not connectedto the cycler (e.g., a prolonged dwell phase for a “day therapy,” i.e.,during the day following a nighttime therapy). At the user's option, thelast fill volume may be selected to be less than the fill volumes usedduring nighttime therapy. The cycler may also optionally prompt the userto select an optional extra last drain to give the user the chance tocompletely empty the peritoneal cavity prior to the infusion of a lastfill volume (which may be carried by the user for a relatively prolongedperiod of time after the end of nighttime therapy). If this function isenabled, the cycler may prompt the user to sit up or stand, or otherwisemove about to mobilize any trapped fluid in the peritoneal cavity duringthis last drain phase.

The cycler may also be programmed to account for an expected amount ofultrafiltration (“UF”) fluid produced during a dwell phase on or off themachine, and to alert the user if a minimum drain volume that includesthe volume infused plus this expected UF is not drained either initiallyat the beginning of therapy, or during a fill-dwell-drain cycle duringtherapy. In an embodiment, the cycler may be programmed for a minimuminitial drain volume and a minimum initial drain time, and to pause orterminate the drain phase if the measured drain flow rate has decreasedbelow a pre-determined threshold value for a pre-determined number ofminutes. The minimum initial drain volume may comprise the volume of thelast fill phase in the preceding nighttime therapy, plus an expected UFvolume from the day therapy dwell phase. If the minimum (or more)initial drain volume is achieved, the minimum initial drain time isreached, and/or the drain flow rate has decreased, the IPV tracked bythe cycler controller may be set to zero at the end of the initial drainphase. If not, the cycler may alert the user. The cycler may allow theuser to bypass the minimum initial drain volume requirement. Forexample, the user may have manually drained at some time beforeinitiating APD. If the user elects to forego adherence to the minimuminitial drain volume, the cycler may be programmed to perform a fulldrain at the end of the first cycle regardless of the type of therapyselected by the user. If enabled, this feature helps to ensure that thesecond fill-dwell-drain cycle begins at an IPV that is as close to zeroas possible, helping to ensure that a prescribed maximum IPV should notbe exceeded during subsequent cycles of the therapy.

The cycler may also be programmed to allow the user to pause therapy.During a pause, the user may have the option to alter the therapy byreducing the fill volume, reducing therapy time, terminating a planned“day therapy,” or ending therapy altogether. In addition, the user mayhave the option to perform an immediate drain at any time duringtherapy. The volume of an unscheduled drain may be selected by the user,whereupon the cycler may resume the cycle at the stage at which it wasinterrupted.

The cycler may be programmed to have a prescriber or “clinician” mode. Asoftware application may be enabled to allow a clinician to create ormodify a set of parameters forming the therapy prescription for aparticular patient or user, as well as setting the limits within which auser may adjust user-accessible parameters. The clinician mode may alsoallow a clinician to fix one or more treatment parameters that wouldotherwise be accessible to a user, as well as lock a parameter toprevent a user from changing it. A clinician mode may bepassword-protected to prevent unauthorized access. The clinician modeapplication may be constructed to interface with a database to read andwrite the parameters comprising a prescription. Preferably, a “usermode” permits a user to access and adjust user-accessible parametersduring a pre-therapy startup phase of a therapy. In addition, an “activetherapy mode” may optionally be available to a user during therapy, butwith access to only a subset of the parameters or parameter rangesavailable in the user mode. In an embodiment, the cycler controller maybe programmed to allow parameter changes during active therapy mode toaffect only the current therapy, the parameter settings being reset topreviously prescribed values before subsequent therapies. Certainparameters preferably are not user-adjustable at all, user-adjustablewith concurrence of a clinician through a prescription setting, oruser-adjustable only within a range of values set by a clinician inprogramming a prescription. Examples of parameters that may not beadjustable solely by the user include, for example, the minimum initialdrain volume or time, maximum initial fill volume, and maximum IPV.User-adjustable parameters may include, for example, the tidal drainfrequency in a cluster (e.g., adjustable between 1 and 5 cycles), andthe percentage of a tidal therapy fill volume to be drained (e.g.,adjustable up or down by a pre-determined amount from a default valueof, for example, 85%). In an alternative embodiment, the clinician modemay allow a clinician to prevent a user from programming a maximum IPVto be greater than a pre-determined multiple (e.g., 200%) of the initialfill volume assigned to a nighttime fill-dwell-drain cycle.

The cycler may also be programmed to routinely alert the user and torequest confirmation when a user-adjustable parameter is entered that isoutside of pre-determined ranges. For example, if the maximum IPV hasbeen made user-adjustable in the clinician mode, the cycler may alertthe user if he or she attempts to select a Max IPV value outside of afractional range (e.g., 130-160%) of the programmed fill volume fornighttime therapy.

The cycler may also be programmed to alert the user (and possibly seekconfirmation) if the initial drain volume has been made user-adjustablein the clinician mode, and the user selects an initial drain volumebelow a pre-determined percentage of the fill volume of the last therapy(e.g., if it is adjusted to be less than 70% of the last fill volume).In another example, the cycler may be programmed to alert the user (andpossibly seek confirmation) if the total expected UF volume has beenmade user-adjustable by the clinician mode, and the user selects a totalexpected UF volume to be below a certain percentage of the total volumeprocessed for a nighttime therapy (e.g., if the total expected UF volumeis set at less than 7% of the total nighttime therapy volume). Generallythe expected UF volume may be determined empirically by a clinicianbased on a user's prior experience with peritoneal dialysis. In afurther embodiment, the cycler may be programmed to adjust the expectedUF volume value according to the actual UF volume in one or morepreceding cycles of a therapy. This volume may be calculated in a CCPDmode by calculating the difference between a measured full drain volumeand the measured fill volume that preceded it. In some cases, it may bedifficult to determine when the peritoneal cavity is fully drained offluid, and it may be preferable to take an average value of thedifference between a full drain volume and a preceding fill volume overa number of cycles.

Some of the programmable treatment settings may include:

-   -   the number of daytime exchanges using the cycler;    -   the volume of solution to be used for each daytime exchange;    -   the total time for a nighttime therapy;    -   the total volume of dialysis solution to be used for nighttime        therapy (not including a last fill volume if a daytime dwell        phase is used);    -   the volume of dialysis solution to be infused per cycle;    -   in a Tidal therapy, the volume of fluid to be drained and        refilled during each cycle (a percentage of the initial fill        volume in a nighttime therapy);    -   the estimated ultrafiltration volume to be produced during a        nighttime therapy;    -   the volume of solution to be delivered at the end of a therapy        and to be left in the peritoneal cavity for an extended period        (e.g., daytime dwell);    -   the minimum initial drain volume required to proceed with a        therapy;    -   the maximum intraperitoneal volume known or estimated to be        present that the cycler will allow to reside in the patient's        peritoneal cavity (which may be based on the measured volumes        introduced into the peritoneal cavity, the measured volume        removed from the peritoneal cavity, and the estimated volume of        ultrafiltration produced during therapy).

Some of the more advanced programmable treatment settings for the cyclermay include:

-   -   the frequency of full drains to be conducted during tidal        peritoneal dialysis;    -   the minimum percentage of the volume delivered to the peritoneum        during a day therapy that must be drained before a subsequent        fill is allowed;    -   prompting the user to perform an extra drain phase at the end of        therapy if a pre-determined percentage of the estimated total UF        is not collected;    -   a minimum length of time required to perform an initial drain        before therapy begins;    -   a minimum length of time required to perform subsequent drains,        either in day-therapy mode or night-therapy mode;    -   variable dwell times, adjusted by the cycler controller to        maintain a fixed total therapy time when either the fill times        or drain times have been changed (thus helping to avoid        disruptions of the user's schedule;

The cycler can provide the user with alerts or warnings about parametersthat have been entered outside a recommended range of values. Forexample, a warning may be issued if:

-   -   the minimum initial drain volume before a therapy is less than a        pre-determined percentage of the currently prescribed last-fill        volume at the end of the previous therapy (e.g., <70%);    -   the maximum IPV is outside a pre-determined percentage range of        the fill volume per cycle (e.g., <130% or >160%);    -   the UF volume threshold to trigger an alert to perform an extra        drain at the end of therapy is less than a pre-determined        percentage of the estimated UF volume per therapy (e.g. <60%);    -   the calculated or entered dwell time is less than a        pre-determined number of minutes (e.g., <30 minutes);    -   the estimated UF volume per therapy is more than a        pre-determined percentage of the total dialysis solution volume        per therapy (e.g., >25%);    -   the sum of all the solution bag volumes for a therapy should be        somewhat greater than the volume of solution used during a CCPD        therapy session, in order to account for priming of fluid lines        and for loss of fluid to drain during air mitigation procedures.

In the clinician mode, in addition to having a selectable maximum IPV,the cycler may be programmed to accept separate minimum drain times forinitial drains, day-therapy drains, and night-therapy drains. In theuser mode or in the active-therapy mode, the cycler may be programmed toprevent a user from skipping or shortening the initial drain phase atthe start of a therapy. In addition, the cycler may permit earlytermination of the initial drain phase only after a series of escalatinglow-drain-flow alerts have been issued. (An initial alert may instructthe user to change positions or re-position the peritoneal dialysiscatheter, which may then be followed by additional alternativeinstructions if low flow conditions persist, up to a maximum number ofalerts). The cycler may also require the user to confirm any change theuser makes to the planned therapy, including bypassing a phase. Theclinician may specify in a prescription setting to prevent the user frombypassing a drain phase during nighttime therapy. During therapy, thecycler controller may be programmed to not reset the IPV to zero unlessthe drain volume exceeds the preceding fill volume (to account for theadditional IPV produced by ultrafiltration). The cycler may also beprogrammed to display to the user the estimated IPV during fills, andmay notify the user if any drain volume exceeds the fill volume by apre-determined amount (e.g. drain volume greater than fill volume plusexpected UF volume). The cycler may also be programmed to identifyerrors in user input and to notify the user of apparent input errors.For example, the number of cycles during a therapy calculated by thecycler, based on the prescription parameters entered by the clinician oruser, should be within a pre-determined range (e.g. 1-10). Similarly,the dwell time calculated by the cycler should be greater than zero. Inaddition, the maximum IPV entered by the user or clinician should begreater than or equal to the fill volume per cycle, plus the expected UFvolume. Furthermore, the cycler may be programmed to reject an enteredvalue for maximum IPV that is greater than a pre-determined amount overthe fill volume per cycle (e.g., maximum IPV ≤200% of initial fillvolume). In some cases, it may be desirable for the cycler to beprogrammed to set the maximum IPV to no greater than the last fillvolume if the solution is to remain in the peritoneal cavity for aprolonged period of time, such as during a daytime therapy. In thiscase, the cycler may be programmed to alert the user if the cyclercontroller calculates that the last drain volume amounts to less than acomplete drain, whereupon the cycler may provide the user with a choiceto terminate therapy or undertake another drain phase.

Managing Increasing IPV while Minimizing Alarms

In an embodiment, the cycler may be programmed to track and manage anincreasing IPV during a therapy without converting the therapy fromcontinuous cycling peritoneal dialysis (“CCPD”) therapy to a standardtidal peritoneal dialysis (“TPD”) therapy, which would fix the residualvolume to a percentage of the initial fill volume. Rather, an adaptivetidal therapy mode may be initiated, in which the residual volume isallowed to fluctuate or ‘float’ in response to any slow-drain conditionsthat may be encountered during any drain phase. The cycler may beprogrammed to permit this mode to operate as long as any subsequent fillvolume plus expected UF does not exceed a prescribed maximum IPV (“MaxIPV”). Thus the dwell-phase IPV may be permitted to increase or decreaseduring a therapy up to a maximum IPV, preferably set by a clinician inthe clinician mode. In this adaptive tidal therapy mode, at each drainphase during a therapy, the cycler continues to attempt a complete drainwithin the allotted time, or as long as a low-flow or no-flow conditionhas not been detected for a prescribed or pre-set number of minutes. Theresidual volume at the end of the drain phase is allowed to vary or‘float’ as long as it does not exceed an amount that would lead toexceeding the maximum IPV in the next fill phase or during the nextdwell phase. In a preferred embodiment, the cycler may be programmed tonot issue an alert or alarm to the user as long as it calculates thatthe subsequent fill phase or dwell phase will not reach or exceedmaximum IPV.

The cycler may be programmed to deliver full fill volumes during eachcycle of a therapy until the cycler controller calculates that the nextfill volume will likely cause the IPV to exceed the maximum IPV. At aconvenient time (such as, e.g., the end of a drain phase), the cyclercontroller may be programmed to calculate a maximum residual IP volume,which represents the maximum permissible residual IP volume at the endof a drain to allow the next cycle to proceed with the previouslyprogrammed fill volume. Partial drains will be permitted by the cyclerwithout alarming or issuing an alert as long as the amount of fluiddrained brings the residual IPV below the maximum residual IPV. If theestimated or predicted IPV at the end of a drain phase is less than themaximum residual IPV, the cycler can proceed with a full fill phase inthe next cycle without risking exceeding the Max IPV. If the estimatedIPV at the end of a drain is greater than the maximum residual IPV, thecycler controller may trigger an alert to the user that the subsequentfill plus UF may exceed the maximum IPV. In an embodiment, the cyclermay display several options for the user to respond to this alert: itmay allow the user to terminate therapy, to attempt another drain phase,or to proceed to enter a revised-cycle therapy mode, in which eachsubsequent fill volume is reduced and one or more cycles are added tothe therapy (thereby ensuring that the remaining volume of freshdialysate is used during that therapy). In an embodiment, a clinician oruser may enable the cycler at the beginning of therapy to automaticallyenter this revised-cycle therapy mode without having to alert the userduring therapy.

In some circumstances, the number of additional cycles may be limited bythe planned total therapy time. For example, the duration of night timetherapy may be limited by the time at which the user is scheduled towake up or to get up to go to work. For nighttime therapy, the cyclercontroller may be programmed, for example, to prioritize the use of alldialysate solution that was planned for therapy in favor of endingtherapy at the scheduled time. If the clinician or user has selected thedwell time to be adjustable, then the cycler controller will (1) add oneor more cycles to ensure that the fill volume plus expected UF does notexceed maximum IPV; (2) ensure that all of the dialysis solution is usedfor therapy; and (3) attempt to reach the targeted end-of-therapy timeby shortening the dwell times of the remaining cycles. An alternativeoption available to the user is to extend the end-of-therapy time. In apreferred embodiment, the cycler is programmed to add one or twoadditional cycles to the therapy to permit a reduced fill volume inorder to prevent exceeding the maximum IPV. The cycler controller isprogrammed to recalculate the maximum residual IPV using the reducedfill volume occasioned by the increased number of cycles. Thus, if a lowflow condition during drain occurs at the same IPV, the new highermaximum residual IPV may permit dialysis to proceed without exceedingmaximum IPV. If the fill volume cannot be reduced enough by adding amaximum allowable number of extra cycles (e.g., 2 cycles in an exemplarynight time therapy scenario), then the cycler may present the user withtwo options: re-attempt a drain phase, or end therapy. The cycler may beprogrammed to reset the fill volume again after an adjustment of thefill volume, possibly adding an additional cycle, if a low flowcondition at the end of drain is again encountered at an IPV above thenewly recalculated and reset maximum residual IPV. Thus the cycler maybe programmed to repeatedly adjust the subsequent fill volumes toprevent exceeding maximum IPV if a premature low flow condition isrepeatedly encountered.

Replenishment Limitation on Dwell Time Reductions

In an embodiment, if the cycler reduces fill volumes by adding one ormore cycles, then it may also reduce the dwell time in order to attemptto keep the therapy session within the total scheduled therapy time.This mode may be useful for nighttime therapy, so that the patient maybe reasonably assured that therapy will have ended before a planned timeof awakening in the morning. However, the cycler will continue toreplenish the heater bag as needed during therapy, the replenishmentgenerally occurring during dwell phases (when the PD cassette is nototherwise pumping to or from the patient). Therefore, in somecircumstances, total therapy time may need to be extended when therequired reduction in remaining dwell times leads to a total remainingdwell time that is less than the total estimated time needed toreplenish the heater bag with the remaining fresh dialysate. The cyclercontroller may therefore calculate a maximum dwell time reductionavailable for the remaining therapy cycles, and extend total therapytime to ensure that the remaining fresh dialysate is properly heated.Because the cycler controller keeps track of the volume of dialysate inthe heater bag, the temperature of the dialysate in the heater bag, andthe volume of remaining fresh dialysate that is scheduled to be infused,it can calculate an estimate of the amount of time needed to replenishthe heater bag to a pre-determined volume (given its intrinsic pumpingcapacity), and the time needed to bring the dialysate in the heater bagup to the prescribed temperature before it is infused into the user. Inan alternative embodiment, the cycler controller may interrupt pumpingoperations to or from the user at any time in order to engage the pumpsfor replenishment of the heater bag. The cycler controller may beprogrammed, for example, to prevent the volume of fluid in the heaterbag from dropping below a pre-determined volume at any time duringtherapy, other than during the last cycle.

In an embodiment, the cycler may be programmed to deliver fluid to theheater bag at a greater flow rate than when it is transferring fluid toor from the user. If binary valves are used to regulate the flow ofcontrol fluid or gas between the positive/negative pressure reservoirsand the control or actuation chambers of the cassette pumps, thecontroller may issue on-off commands to the valves at different pressurelevels measured in the control or actuation chambers of the pumps. Thusthe pressure threshold in the pump control or actuation chamber at whichthe controller triggers an ‘off’ command to the binary valve may have anabsolute value that is greater during delivery to or from the heater bagthan the corresponding pressure threshold when the cycler is deliveringor pulling fluid to or from the user's peritoneal cavity. A higheraverage pressure applied to the pump membrane may be expected to resultin a greater flow rate of the liquid being pumped. A similar approachmay be used if variable orifice valves are used to regulate the flow ofcontrol fluid or gas between the pressure reservoirs and the control oractuation chambers of the cassette pumps. In this case, the controllermay modulate the flow resistance offered by the variable orifice valvesto maintain a desired pressure in the pump control chamber withinpre-determined limits as the pump membrane is moving through its stroke.

Exemplary Modes of Therapy

FIG. 176 is a graphical illustration (not to scale in either volumes ortime) of an adaptive tidal mode of the cycler when in a CCPD mode. Theinitial drain at the beginning of therapy is omitted for clarity. Themaximum IPV (Max IPV) 700 is a prescription parameter preferably set bythe clinician. The initial fill volume 702 is also preferably set by theclinician as a prescription parameter. The expected UF volume isrepresented by the additional IPV increase 704 during the dwell phase706. The expected UF volume for an entire therapy may be entered by aclinician into the prescription, and the cycler may then calculate thedwell time per cycle based on the number of cycles during the therapy,and thus the expected UF volume per cycle. It should be noted thatultrafiltration is expected to occur throughout the fill-dwell-draincycle, and the expected UF volume may include the volume of fluidultrafiltered throughout the cycle period. In most cases, the dwell timeis much larger than the fill or drain times, rendering theultrafiltration volumes during fill or drain relatively insignificant.The fill and drain times may be adjustable by altering the pressure setpoints used by the controller to regulate the control valves between thepressure reservoirs and the pumps. However, the adjustability of liquiddelivery flow rates and pressures to the user is preferably limited inorder to ensure user comfort. Thus the expected UF volume per cycle 704may be reasonably representative of ultrafiltration during the cycle.The drain phase 708 of the cycle in this example is a full drain, aswould occur in a CCPD mode of therapy.

The maximum residual volume 710 can be calculated by the cyclercontroller once the Max IPV 700, the initial fill volume 702, and theexpected UF volume are entered by the clinician. The maximum residualvolume 710 is an indication of the ‘headroom’ 712 available in theperitoneal cavity to accommodate more fluid before reaching Max IPV 700.In an adaptive tidal mode within a CCPD mode of therapy, as long as adrain volume 714, 716 leaves an estimated residual volume 718, 720 lessthan the maximum residual volume 710, the subsequent fill volume 722,724 can remain unchanged, because Max IPV 700 is not expected to bebreached. As shown in FIG. 176, the occurrence of a low flow conditionat the residual volumes 718 and 720 triggers the cycler to initiate thenext fill phase 722 and 724. During this form of therapy, the cyclerwill continue to attempt to perform a full drain 726 within an allottedtime assuming a low-flow or no-flow condition is not encountered beforethe estimated zero IPV is reached. Thus, even if a full drain is notperformed (because of a low-flow or no-flow condition), in this case,full fill volumes will continue to be infused, the residual IPV will beallowed to float within a pre-determined range, and the user preferablywill not be disturbed by any alarms or alert notifications.

FIG. 177 is a graphical illustration of how the cycler may handleincomplete drains that fail to reach the maximum residual IPV 710. Inthis case, the drain phase 730 of the third cycle encounters a low-flowor no-flow condition that prevents the cycler from draining theperitoneal cavity below the maximum residual IPV 710. Given theestimated residual volume 732 (the estimated residual volume after apre-determined duration of a low-flow condition), the cycler calculatesthat a subsequent fill phase volume 734 will likely cause the prescribedMax IPV 700 to be reached or exceeded 736. Therefore, at the end ofdrain phase 730, the cycler may alert the user to this issue. The usermay then have the option to terminate therapy, instruct the cycler tore-attempt a drain phase (after possibly changing positions orrepositioning the PD catheter), or instruct the cycler to enter into arevised-cycle therapy mode in which the subsequent fill volumes arereduced and one or more cycles added to complete the therapy with theplanned total volume of dialysate. To keep within the allotted orprescribed total therapy time, the cycler can calculate the duration ofthe modified cycles by reducing the fill and drain times to account forthe reduced fill and drain volumes, and then determining whether and howmuch the dwell times need to be reduced to meet the designated endingtime of the therapy session.

A user may optionally enable a revised-cycle mode of CCPD at thebeginning of a therapy, so that the occurrence of a low-flow conditionduring therapy can trigger the revised-cycle mode without disturbing theuser with an alert or alarm. Otherwise, the user may select therevised-cycle mode upon the occurrence of a low-flow condition above themaximum residual IPV. If the user elects to enter a revised-cycle mode,the cycler controller may calculate the required fill volumes for eachof an additional one, two or more cycles (remaining fill volume dividedby the remaining planned cycles plus the additional one or more cycles).If one additional cycle yields a fill volume (plus expected UF) lowenough to avoid reaching or exceeding Max IPV, the cycler (eitherautomatically or at the user's option) will resume CCPD at that new fillvolume 738. Otherwise, the cycler controller will calculate a new fillvolume based on an additional two cycles of therapy. (Rarely, more thantwo additional cycles may be required to ensure that Max IPV is notbreached during the remaining therapy. If the additional cycles requirea substantial reduction in the remaining dwell times, the cycler mayalert the user, particularly if a minimum dwell time has beenprescribed, or heater bag replenishment limitations will require alengthening of the total therapy time). The now-reduced fill volume 738allows the cycler controller to re-calculate a revised maximum residualIPV 740, which is a function of the sum of the new fill volume plus theexpected UF volume per cycle. Any subsequent drain phases that leave anestimated residual IP volume less than the revised maximum residualvolume 740 will preferably not trigger any further alerts or alarms tothe user, allowing for the adaptive mode of tidal therapy to remainenabled. In an embodiment, the cycler may re-calculate the expected UFvolume if it has reduced the duration of the remaining dwell phases inorder to stay within the planned total therapy time. Any re-calculatedreduction in the expected UF volume may further increase the revisedmaximum residual IPV. In the example shown in FIG. 177, the cyclercontinues to perform CCPD mode therapy, and happens to be able to drainfully in the remaining cycles. In order not to further inconvenience theuser, the cycler may optionally refrain from making any furtheradjustments to the therapy (particularly if the total volume ofdialysate and the total therapy time have been kept within theprescribed parameters).

FIG. 178 illustrates that a planned standard tidal peritoneal dialysis(TPD) therapy may also be subject to a revised-cycle mode of TPD therapyif the cycler controller calculates that the user's Max IPV 700 islikely to be reached or exceeded during therapy. In this example, a useror clinician has selected a standard tidal therapy, in which a plannedresidual IP volume 742 (in actual volumetric terms or as a percentage ofthe initial fill volume) has been selected. As an optional feature ofthe cycler, the user or clinician has also chosen to perform a completedrain 744 after every three tidal fill-dwell-drain cycles, comprising acycle cluster during a therapy session. In this example, a low-flowcondition preventing draining below the maximum residual volume 710occurs at the end of the third cycle 746. At the option of the user orclinician, the cycler either alerts the user to choose to end therapy,repeat a drain phase, or initiate a revised-cycle TPD therapy, or thecycler is allowed to automatically initiate a revised-cycle TPD therapy.In this case, the addition of a sixth cycle with a consequent reductionof the fill volume to a revised fill volume 748, is sufficient to avoidexceeding the Max IPV 700, which otherwise would have occurred 750. Inthis example, the cycler proceeds to perform a complete drain 744 at theend of a cluster, but resumes a standard TPD therapy thereafter. If theplanned residual volume has been specified to be a percentage of theinitial fill volume of the cluster, then that percentage may be appliedto a revised residual IPV 752. The cycler may then calculate thesubsequent drain volumes 754 by calculating the appropriate fraction ofthe revised fill volume 748 plus expected UF volume in order to drain tothe revised residual IPV 752. Any subsequent fill volumes 758 may remainsimilar to the revised fill volume 748, as long as the cycler calculatesthat the Max IPV 700 will not be breached. Alternatively, the subsequentfill volumes may be reduced in a manner designed to maintain arelatively constant revised dwell-phase IPV 756. In this case, thecycler controller may be programmed to make the additional calculationsnecessary to ensure that the entire remaining dialysate solution will beproperly divided among a revised fill volume 748 and later fill volumesreduced to maintain a revised dwell-phase IPV 756. In an alternativeembodiment, the clinician or user may select the prescribed residual IPvolume 742 to be relatively fixed volumetrically throughout therapy. Inthis case, the cycler controller may convert the percentage value of theresidual IP volume 742 into a volumetric value (e.g. in milliliters),and continue to use that targeted residual volume after therevised-cycle mode has been instituted. In any event, the cyclercontroller may continue to apply the Max IPV 700 limitation incalculating any revised fill volumes.

FIG. 179 illustrates how an adaptive tidal therapy mode may be employedduring a standard tidal therapy. In this example, a slow-drain condition760 is encountered below the maximum residual volume 710. As an optionalfeature of the cycler, the user or clinician has also chosen in thisexample to perform a complete drain 764 after every four tidalfill-dwell-drain cycles, comprising a cycle cluster during a therapysession. In this case, the cycler calculates that the Max IPV 700 willnot be reached if the tidal fill volume 762 is maintained. The cyclermay be programmed to continue the tidal therapy at a revised residual IPvolume 760 in order to avoid another slow-drain condition.Alternatively, the cycler may be programmed to attempt to drain back tothe previously prescribed residual IP volume 742. Since tidal therapycan continue without risk of breaching Max IPV 700, the user need not bealerted to the institution of a revised or floating residual volume ofthe adaptive tidal therapy mode. A full drain 764 is initiated asprescribed, and if successful, the cycler controller may re-institutethe originally prescribed tidal therapy parameters. In an embodiment,the cycler may be programmed to alert the user if a full drain cannot beachieved at the end of a tidal therapy cluster.

Adaptive Filling

In some scenarios, variations or alterations from a programmed therapymay cause a cycler to be unable to complete the therapy as prescribed.For example, if more solution volume is used than anticipated during atherapy and the number cycles programmed for the therapy, “n”, ismaintained, the last fill of the therapy may not be completed asprescribed, because there is not enough solution available to completeat least one fill in the therapy. (Generally, a fill volume must besufficient to result in a minimum volume of intra-peritoneal fluidduring a dwell phase). In one example, the cycler may be programmed toadjust each fill cycle volume to ensure that a minimum amount of fluidvolume resides in the peritoneal cavity during each dwell phase. A fillvolume may need to be greater than anticipated, for example, if a priorfluid drain volume exceeds the expected amount (for example, through theaction of the user during therapy), or if the controller exceeds theanticipated drain volume during a previous cycle to avoid exceeding thepre-programmed Max IPV or a newly adjusted Max IPV. In this case, asubsequent fill volume may be greater than anticipated to maintain thepre-determined dwell volume for that cycle. This may potentially reducethe amount of solution available for the last cycle to a fill volumethat will fail to provide the required intraperitoneal dwell volumeduring the last cycle.

To avoid these scenarios, during a therapy, the cycler controller maycommand that at least one cycle be dropped from the number of cyclesprogrammed for the therapy. Thus, the number of cycles that will occurover the therapy will then be one or more less than “n”. A cycle may bedropped, for example, if a fractional or non-integer number of cyclesare calculated for a therapy, either at the beginning of therapy or atany time during the therapy. Additionally, it may occur if a userperforms a drain during a tidal therapy that deviates from theprogrammed tidal percentage and/or modulus for the therapy. For example,a user may elect to perform a full drain during a tidal therapy. Thecontroller may then drop a cycle because there may no longer be enoughremaining dialysate in the solution bags to complete every programmedcycle of the therapy.

In the event that a cycle is dropped from therapy, the expected timesfor remaining phases of the therapy may be adjusted, for example, toincrease the expected dwell times. This increase in expected dwell timesmay allow for a larger volume of UF to accumulate in the peritonealcavity. Ultrafiltration may increase due to the infusion of freshsolution into the peritoneal cavity, when, for example, a user performsa full drain during a tidal therapy, and the peritoneal cavity issubsequently refilled to the initial fill volume with fresh solution.The concentration gradient for certain solutes will be greater and mayresult in more ultrafiltration during the dwell phase. Additionally, ifthe controller calculates expected UF per cycle based upon apreprogrammed expected total UF over the therapy, dropping a cycle maycause the controller to recalculate and expect a greater UF volume percycle. In an embodiment, the controller may recalculate expectedultrafiltrate volume values for the remaining cycle(s) after a cycle isdropped from the therapy, accounting for any reduction in total therapytime, and optionally accounting for increased ultrafiltration from theuse of a fresher solution earlier in the therapy.

In some scenarios, this increase may be sufficient to cause ananatomical reservoir volume, or in the specific example, anintraperitoneal volume (IPV) of the patient to exceed a preprogrammedmaximum volume during a cycle. This is more likely to occur if the MaxIPV volume is set unusually low. Though some embodiments may avoid sucha scenario by calculating per cycle UF once at the beginning of therapy,it may be preferable to use an adaptive fill volume which is responsiveto such therapy changes. In some embodiments, the number of cycles inthe therapy may be kept at the programmed number, “n”. The fill volumefor the remaining cycles would then be altered from the programmed fillvolume for the therapy to ensure that the Max IPV threshold is notexceeded.

FIG. 180 depicts an example plot 5390 which shows the peritonealreservoir volume over time for a tidal therapy. The plot is depicted forillustrative purposes and is not to scale. The example tidal therapy isprogrammed to have a total therapy volume of 2000 mL, an initial fillvolume of 1000 mL, and a tidal percentage of 50%. The total expected UFfor the therapy is set at 750 mL. The maximum IPV volume 5392 is set at1400 mL. The therapy is programmed or calculated to have a total ofthree cycles. In FIG. 180, the therapy proceeds as programmed without acycle being dropped.

An initial drain 5394 is performed and brings the patient IPV down to 0mL. The initial fill 5396 of 1000 mL is then delivered to the peritonealcavity. As shown, the IPV rises after the fill is complete due to the UFvolume 5398 accumulating in the peritoneal cavity of the patient. In theexample embodiment, 250 mL of UF accumulates per cycle. Though theexample plot 5390 appears to depict the UF as accumulating during dwellphase, this is for illustrative purposes only. In reality, this UF wouldaccumulate continuously over the fill, dwell, and drain.

When the first dwell 5400 is completed, 50% of the initial fill volumeand the expected UF is drained from the patient in the drain 5402 of thefirst cycle. This brings the patient IPV to 500 mL. A fill 5404 of 500mL is then pumped to the patient to bring the patient up to a 1000 mLIPV for the dwell 5406 of the next cycle. When the dwell 5406 completes,this drain and fill process is repeated with drain 5408 and fill 5410.After the dwell 5412 of the last cycle, the patient is fully drained toempty in drain 5414. The total volume delivered over the therapy is 2000mL as programmed. The maximum IPV threshold 5392 is also not breached atany time during the therapy.

FIG. 181 depicts an example plot 5420 which shows the peritonealreservoir volume over time for a tidal therapy. This therapy isprogrammed to have the same parameters as that shown in FIG. 180. Theplot 5420 is shown with solid and dashed lines. The solid lines indicateportions of the plot 5420 where the therapy is the same as in FIG. 180.The dashed lines indicate where the plot 5420 departs from the plot 5390shown in FIG. 180.

To start, an initial drain 5422 drains the patient to empty and then aninitial fill 5424 delivers 1000 mL to the patient as in FIG. 180. Thisleaves 1000 mL of the total therapy volume remaining for the rest of thetherapy. While the first dwell 5426 is occurring the 250 mL of UFaccumulates. This leaves an expected UF volume for the remaining portionof the therapy of 500 mL.

During the therapy in FIG. 181, a user elects to perform a full drain5428 after the first dwell 5426. At the end of the full drain 5428, thepatient is left in an empty state. The cycler then fills the patient inthe second fill 5430 of the therapy. This fill 5430 delivers 1000 mL ofsolution to the patient in order to keep the dwell volume at theprogrammed amount. After the second fill 5430, the programmed 2000 mLtherapy volume has been used and there may be no more solution remainingto deliver to the patient. As a result, in the example embodiment, thiscauses a cycle to be dropped from the therapy, shortening the therapy totwo cycles. In turn, the remaining expected UF volume of 500 mL is thenpreferably redistributed to the remaining fill-dwell phase of the secondcycle. As shown, this causes the Max IPV threshold 5392, which in thisexample is set at 1400 mL, to be crossed (fill volume+UF=1500 mL).

In some embodiments, the cycler controller may be configured torecognize and adapt to such a scenario before it occurs. This may beaccomplished by having the controller compute before dropping a cycleand performing a fill that the current patient volume plus the next fillvolume and the expected UF per cycle does not exceed the Max IPVthreshold 5392. If the calculation indicates that the max IPV threshold5392 will be exceeded, the controller may alter the fill volume so thata breach of the Max IPV threshold 5392 is avoided. This may result inmaintaining the “n” number of fills programmed for the therapy (in thisexample, 3 fills).

The fill volume may be adapted or changed from the originally programmedvolume such that the remaining therapy volume is spread out over theremaining cycles. This may ensure that the fill volume and the expectedUF accumulated during a cycle does not exceed the Max IPV threshold5392. It may also ensure that the full therapy volume of dialysatesolution is used. By using the full therapy volume, waste of solutionstaged for use during the therapy is minimized. The user may be promptedto acknowledge or confirm acceptance of the newly calculated adaptedfill volume. In other embodiments, a user may be presented with one ormore options to change the therapy, each of which will avoid exceedingthe max IPV threshold 5392. The user may select a desired option. Theoptions need not be limited to those described herein.

The following equation may be used to determine an adapted fill volumefor a cycle:V _(T)=(V _(NEW)*Full Fills Remaining)+((Tidal %*V _(NEW))*Tidal FillsRemaining)

Where V_(T) is equal to the Therapy Volume Remaining and V_(NEW) isequal to the new fill volume or adapted fill volume for the cycle.

The equation may be rearranged to solve for V_(NEW) to determine theadapted fill volume. Using the example therapy in FIG. 181, when it isdetected that a non-adapted fill volume will cause the Max IPV threshold5392 to be exceeded, V_(NEW) may be determined as follows:1000 mL=(V _(NEW)*1)+((0.5*V _(NEW))*1)

Which simplifies to:1000 mL=1.5 V _(NEW)

Which may be rearranged to solve for V_(NEW):V _(NEW)=1000 mL/1.5=666.6 mL

The above equation assumes that the tidal percentage is maintained inthe remaining cycles of the therapy volume. Optionally, the equation mayallow for the tidal percentage to be changed in the remaining cycles ofthe therapy.

FIG. 182 depicts an example plot 5350 showing the intraperitoneal volumeover time for a tidal therapy. The therapy parameters are the same asthose programmed in FIGS. 180 and 181. As shown, the fill volume isadapted after a user initiated full drain 5452. The adapted fill volumeensures that the max IPV threshold 5392 is not exceeded during thetherapy and that the entirety of the programmed therapy volume isconsumed. A cycle is not dropped, as dropping the cycle would not allowthe full therapy volume to be used without exceeding the max IPVthreshold 5392. Additionally, the tidal percentage is kept at theprogrammed value in the example plot 5350 shown in FIG. 182.

In some embodiments, a cycle may be dropped and a calculation may thenbe made to determine if the max IPV threshold 5392 will be breached. Thedropped cycle may then be brought back so that the programmed number ofcycles for the therapy is maintained. Alternatively, the calculation maybe made preemptively before dropping the cycle to determine if droppingthe cycle will cause the max IPV threshold 5392 to be exceeded.

Referring back to FIG. 182, calculated above as V_(NEW), the second fill5454 is 666 mL (rounded for convenience). The 250 mL of UF 5398accumulated during the cycle does not then cause the max IPV threshold5392 to be exceeded. During the second drain 5456 the tidal percentageis kept at 50% and the patient is drained to 333 mL. The fill 5458 ofthe last cycle of 333 mL brings the patient's IPV back to the calculatednew fill volume, V_(NEW). Again, the UF 5398 for the last cycle is ableto accumulate without the max IPV threshold 5392 being exceeded. Thepatient is then drained to empty in the drain 5460 of the last cycle toconclude the therapy.

In some embodiments, the controller may adjust the tidal percentage mayto keep the IPV of the patient closer to the initial fill volume.Alternatively, in some embodiments the tidal therapy may be converted toa non-tidal therapy after the first adapted fill volume is delivered tothe patient. For example, the first adapted fill may be delivered andthe dwell may be allowed to elapse. In the following drain, a cycler mayonly drain the expected UF for the cycle and the therapy may enter a UFmaintenance mode. In some embodiments, the expected UF plus an optionalextra margin of fluid may be drained. This may allow the next fill tobring the IPV of the patient back to approximately the initial fillvolume. Again this should allow for the full therapy volume to be usedwithout the max IPV threshold 5392 for the therapy being exceeded. Inanother embodiment, the tidal therapy may be converted to a CCPD therapywith the remaining solution volume split between a number of cycles.

In some embodiments, the fill volume may be adapted while still droppinga cycle from the therapy. In such scenarios, the fill volume may belowered such that the expected UF per cycle after a cycle is droppeddoes not cause the max IPV threshold 5392 to be exceeded. In someembodiments, the fill volume may be recalculated as:V _(NEW)=Max IPV−(Expected UF+Optional Margin)

Using this equation and referring to the example therapy described inFIG. 181, after the user elects to perform a full drain, the fill volumemay be recalculated based on the new expected UF after the last cycle isdropped. The fill volume may be changed to 825 mL (15% margin onexpected UF). Thus the therapy may be completed without the max IPVthreshold 5392 being breached. In such embodiments, some solution willbe unused at the end of the therapy.

In addition to implementing an adaptive fill volume, the controller canoptionally be programmed to perform a fill volume less than thepreviously programmed fill volume (a ‘shorted fill’). This can beuseful, for example, if the number of calculated cycles is a non-integernumber, which can occur if a programmed therapy volume does not divideevenly into a number of defined cycles. The therapy may perform ashorted fill on the last cycle if a predetermined percentage (e.g. 85%)of the programmed fill volume is available. If the predeterminedpercentage is not available, the controller can drop the cycle and leavethe extra solution unused.

In some cases, if more solution than expected is used during a portionof the therapy, then the remaining solution volume for the last cyclemay fall below a predetermined percentage threshold. This can occur inresponse to a number of factors, such as tolerances in volume targeting(e.g. a small over-delivery may be allowed). Consequently, thecontroller may drop the last programmed cycle in response, and mayreconfigure the remaining dwell phases to increase the expected UF percycle. this could cause the Max IPV threshold 5392 to be exceeded.

In some embodiments, this situation may be avoided by preventing thecycler controller from dropping the last cycle of the therapy. Theremaining volume in the attached bags may be delivered to the patientfor the last fill regardless of what percentage of the programmed fillvolume is remaining. Alternatively, if the therapy is a CCPD therapy,the therapy may be converted to a tidal therapy. The tidal percentagemay be selected so that the programmed fill volume is maintained withoutdropping a cycle.

In some embodiments, such a scenario can be avoided by performing theshorted fill at the beginning of therapy (e.g. during the first fill).This may ensure that the remaining therapy volume may be divided betweenthe remaining cycles so that substantially the full programmed fillvolume may be delivered to the patient during each cycle. Thus the lastfill volume will be expected to be all or nearly all of the programmedfill volume instead of a volume closer to the predetermined percentagethreshold. This effectively creates a buffer volume. Whether the lastfill cycle is still performed may still be subject to the predeterminedpercentage of the programmed fill volume threshold. But the likelihoodof the threshold not being met may be reduced, owing to theimplementation of the buffer fill volume.

The controller can optionally be programmed to assign a range to thethreshold fill volume, as a percentage of a programmed fill volume. Thisrange may be viewed as a hysteresis band placed around the predeterminedpercentage of programmed fill volume threshold. This hysteresis band canbe useful in accomodating small differences between expected volume usedand actual volume used during a therapy. The controller may beprogrammed to apply a hysteresis band as a range of percentage values oneither or both sides of the predetermined percent threshold. In someembodiments, this hysteresis band may be clinician or user programmable.

Pump Operation Synchronization

In various embodiments, during pumping, pump chambers of a cassette maybe synchronized. The following description of pump operations may applyto any device that operates a pump cassette having two or more pumps. Inan embodiment, such a device may be, for example a peritoneal dialysiscycler. In other embodiments, it may be an intravenous infusion pumpsystem or an extracorporeal circulation pumping system using a pumpcassette (such as, e.g., a hemodialysis or cardiopulmonary bypasssystem), or another type of pumping system using a pump cassette.Exemplary systems in which the following pump synchronizing operationsmay be implemented include for example, the peritoneal dialysis systemsdisclosed in U.S. Pat. Nos. 5,350,357, 5,431,626, 5,438,510, 5,474,683and 5,628,908. They may also include, for example, the hemodialysissystem disclosed in U.S. Pat. Nos. 8,246,826, 8,357,298, 8,409,441 and8,393,690. They may also include, for example, the cardiopulmonarybypass systems disclosed in U.S. Pat. No. 8,105,265. In the followingdescription, the term cycler is intended to encompass other pumpingdevices (such as those noted above) that may incorporate the use of apump cassette.

A number different synchronization schemes may be used. Suchsynchronization schemes may serve to temporally dictate when varioussteps of a pumping operation occur (i.e. the filling and delivery of acassette pumping chamber and any associated volume measurements,venting, etc.). Additionally, such synchronization schemes may serve totemporally structure pumping operations occurring across multiplepumping chambers of a cassette.

In some embodiments, pumping operations may use differentsynchronization schemes when different tasks are being performed. Forexample, a first type of chamber synchronization scheme may be used whendraining fluid from a patient, while a second type of chambersynchronization scheme may be used when emptying a remaining dialysatevolume from a heater bag (or other reservoir) after a therapy hasconcluded. The synchronization scheme selected may be optimized forhandling relatively large throughputs of fluid volume. Thesynchronization scheme may also be optimized to minimize patientdiscomfort. Depending on the task being performed, one or more of anumber of synchronization schemes may be assigned to each differentpumping operation as appropriate.

FIG. 183 depicts a flowchart detailing a number of example steps whichmay be used to synchronize pumping operations in a two-chamber pumpcassette. As shown in the example embodiment, the flowchart depicts asynchronization scheme for a two-chamber cassette, although theprocedure may readily be generalized for a multi-chamber cassette. Forexample, a similar scheme may be used for a cassette with additionalpump chambers (e.g. sets of chambers ganged together such that theyoperate in parallel). As shown, at step 4000, the controller may causeChamber A to execute a fill step. A fill step entails subjecting thetarget chamber of the cassette to a negative pressure while that chamberis in fluidic communication with a desired source reservoir. In someembodiments, the negative pressure may be applied for a predeterminedtime period sufficient to substantially fill the target chamber. If onlya partial fill volume is desired, then the cycler controller mayestimate any desired pump fill volume by calculating a relationshipbetween the fill volume and the time taken to reach that fill volumethrough a series of volume measurements at periodic intervals during afill cycle.

In step 4002, the device or cycler (via a device controller) may thenmake a measurement of the volume which was filled in Chamber A. Any typeof volume measurement means may be used to perform this step, including,for example, pressure measurements in relation to a reference chamber(FMS), acoustic volume sensing, pump membrane position sensing, etc. Asshown in FIG. 183, an FMS-type measurement may be used, including any ofthe FMS methods described herein. The measurement of the current volumein the chamber may be compared to a previous measurement (e.g. thevolume measurement taken after a preceding delivery) to determine thevolume with which the chamber was filled. Additionally, in someembodiments, this measurement may be an indirect measurement from whichthe current volume may be inferred, such as, for example: the time spentin the fill mode before measurement as a percentage of a reference timerepresenting complete filling; optical, ultrasonic or electricalcapacitive detection or estimation of the relative position of the pumpmembrane in the pumping chamber, as an indication of the percentage of afull liquid volume when the membrane is fully retracted; or a variationin the pressure waveform detected as the pump membrane travels throughits excursion, modeled against an empirically determined referencevariation during testing. At about this time, the cycler may also beginstep 4004, the filling of Chamber B.

The cycler may deliver the volume contained in Chamber A to a desireddestination in step 4006. A deliver step may entail subjecting thedesignated chamber of the cassette to a positive pressure while thatchamber is in fluidic communication with a desired destinationreservoir. In some embodiments, the positive pressure may be applied fora predetermined time period sufficient to substantially deliver most orall of the volume of the designated chamber. After delivering Chamber A,in step 4008, the cycler may then make a measurement of the volume whichwas delivered by Chamber A during step 4006. In some embodiments,measurement of the current volume in the chamber may be compared to aprevious measurement (e.g. the volume measurement taken in step 4002) todetermine the volume delivered from Chamber A. Chamber B may continue tofill as steps 4002, 4006, and 4008 are completed.

As shown, after step 4008 is completed, the cycler may wait for apredetermined time period to elapse before Chamber A is refilled. Thisperiod of time may be selected so that it is about equal to the amountof time which will be needed to complete step 4004, which can bedetermined empirically, for example, through a series of pumping stepsat the beginning of a therapy.

After filling of Chamber B is complete, in step 4010, the cycler maythen make a measurement of the volume which was filled in Chamber Bduring step 4004. In some embodiments, this may take place while ChamberA is waiting for the predetermined time period to elapse, oralternatively at the end of the time period. Thus, while the measurementis being taking in step 4010, Chamber A may return to step 4000 andbegin refilling.

The cycler may then deliver the volume in Chamber B in step 4012. Step4012 may occur while Chamber A is refilling. After delivering fromChamber B, in step 4014 the cycler may then make a measurement of thevolume which was delivered from Chamber B during step 4012. Again, thismay occur as Chamber A is refilling.

As shown, after step 4014 is completed, the device may wait for apredetermined time period to elapse before Chamber B is refilled. Thisperiod of time may be selected so that it is about equal to the amountof time which will be needed to complete step 4000. After Chamber A hasfinished refilling, the device may, as described above, take ameasurement of the volume refilled in step 4002. At this point, thedevice may return to step 4004 and being refilling of Chamber B. Theexample steps in the flowchart may repeat as necessary until a desiredtask is complete (e.g. patient is drained to empty).

FIG. 184 depicts another embodiment for synchronizing pumping operationsin a two-chamber cassette. As shown in the example embodiment, theflowchart depicts a synchronization scheme for a two-chamber pumpcassette, although the procedure can readily be generalized for use on acassette with additional chambers (e.g. sets of chambers ganged togethersuch that they operate in parallel). As shown, at step 4020, the devicemay cause Chamber A to execute a fill step. In step 4022, the device maythen make a measurement of the volume which was filled in Chamber Aduring step 4020. As before, any type of suitable sensor or suitablemeasurement means may be used to perform this step. As shown in FIG.184, an FMS-type measurement, such as any of those described herein maybe used. In other embodiments, and as previously noted, acoustic volumesensing or any of other suitable measurement means may be used. Thecycler may then deliver the volume contained in Chamber A to itsdestination in step 4024. At this time, the cycler may also begin step4028, the filling of Chamber B. After delivering Chamber A, in step4026, the cycler may make a measurement of the volume which wasdelivered from Chamber A during step 4024. Chamber B may continue tofill as steps 4024 and 4026 are completed.

As shown, after step 4026 is completed, the cycler may check to see thatthe volume in Chamber A was appropriately delivered. This may, forexample involve comparing the measurements from steps 4022 and 4026. Thecycler may use this comparison to determine whether a predeterminedamount or proportion of the fill volume was delivered. When thepredetermined amount or proportion of the fill volume is delivered, thecycler may consider the chamber fully delivered. In the event that thecycler determines that the Chamber A volume was not fully delivered, thecycler may perform steps 4024 and 4026 again. These steps may berepeated until the cumulative volume from each attempt falls within thepredetermined amount or proportion of the measurement from step 4022. Insome embodiments, there may be a limit to the number of times thesesteps may be repeated before the cycler proceeds to the next step andattempts to deliver Chamber B. In some embodiments, once this limit isreached, and if a predetermined amount of fluid has not been delivered,an occlusion alarm or the like may be triggered by the cyclercontroller.

After it has been determined that Chamber A has been fully delivered,step 4030 may be performed. In step 4030, the cycler may make ameasurement of the volume which was filled into Chamber B during step4028. Additionally, after it is determined that the full volume ofChamber A has been fully delivered (or a retry limit has been reached)the cycler may check to see if a predetermined period of time haselapsed. In the event that the predetermined period of time has notelapsed, the cycler may wait for the remainder of the predetermined timeperiod to elapse before Chamber A is refilled. This period of time maybe selected such that it is about equal to the amount of time which willbe needed to complete step 4028. Step 4032 may also be performed afterthe predetermined period of time has elapsed. It may be desirable thatstep 4032 begin after Chamber A has begun being refilled.

After delivering Chamber B, in step 4034, the cycler may then make ameasurement of the volume which was delivered from Chamber B during step4032. Chamber A may continue to fill as steps 4032 and 4034 arecompleted.

As shown, after step 4034 is completed, the cycler may check to see thatthe volume in Chamber B was fully delivered. This may, for exampleinvolve comparing the measurements from steps 4030 and 4034. The cyclermay use this comparison to determine whether a predetermined amount orproportion of the fill volume was delivered. In the event that thecycler determines that the Chamber B volume was not fully delivered, thecycler may perform steps 4032 and 4034 again. These steps may berepeated until the cumulative volume from each attempt falls with thepredetermined amount or proportion of the measurement from step 4030. Insome embodiments, there may be a limit to the number of times thesesteps are repeated before the device proceeds to a next step andattempts to deliver Chamber A. If a limit exists, once it is reached, anocclusion alarm or the like may be triggered by the system controller.In other embodiments, once this limit is reached, the cycler may enter atroubleshooting mode to test for various conditions (e.g. an occlusion)and issue an alert or alarm if necessary. After it has been determinedthat Chamber B has been fully delivered, step 4022 may be performed. Instep 4022, the cycler may make a measurement of the volume which wasfilled into Chamber A during step 4020. Additionally, after it isdetermined that the full volume of Chamber B has been fully delivered(or a limit of attempts has been reached) the cycler may check to see ifa predetermined period of time has elapsed. In the event that thepredetermined period of time has not elapsed, the cycler may wait forthe remainder of the predetermined time period to elapse before ChamberB is refilled. This period of time may be selected such that it is aboutequal to the amount of time that will be needed to complete step 4020.Step 4024 may also be performed after the predetermined period of timehas elapsed. Step 4024 preferably may begin after the refilling ofChamber B has begun. The example steps in the flowchart may be repeatedas necessary until a desired task is complete (e.g. patient is drainedto empty). FIG. 185 depicts a flowchart detailing another embodiment forsynchronizing pumping operations in a two-chamber cassette.Specifically, the flowchart shown in FIG. 185 depicts a number ofexample steps that may be followed to synchronize delivery of fluid froma two-chamber pump cassette, although the scheme may readily begeneralized for use in a cassette with additional chambers (e.g. sets ofchambers ganged together such that they operate in parallel). Theflowchart depicted in FIG. 185 begins after each of Chamber A andChamber B has been filled and an initial measurement of the fill volumeshas been taken.

As shown, in the example delivery synchronization scheme, the chambersdeliver their volumes one after the other in sequential fashion.Starting at step 4040, Chamber A may deliver its volume to the desireddestination. The cycler may then conduct a measurement of the volumedelivered in step 4042. This measurement may be compared to the initialfill volume measurement to determine how much of or if the entire volumewas delivered.

In the example flowchart, steps 4044, 4046, 4048, 4050 are shown indashed outline form. These steps are optional and may not be included inall embodiments. In some embodiments, the cycler may not deliver thevolume in a chamber all at once. Instead, in some embodiments, multipledelivery and measurement steps may occur before the entire volume isdelivered from the chamber. In this case, steps 4044, 4046, 4048, 4050provide additional delivery and measurement steps sufficient to deliverthe entire chamber volume. In some embodiments, a greater or lessernumber of delivery and measurement steps may be used.

Additionally, in some embodiments, the cycler may attempt to deliver achamber volume multiple times in the event that the measurement taken in4042 is lower than desired or indicates that the chamber was not fullydelivered. In this case, steps 4044, 4046, 4048, 4050 may be performedas needed until the entire chamber volume has been delivered. In someembodiments, additional steps may be added to allow the cycler todeliver the entire chamber volume. In some embodiments, there may be alimit to the number of delivery and measurement steps that may beperformed before the cycler stops trying to deliver and proceeds to acton the next chamber. In the example embodiment, after completingdelivery from Chamber A, the cycler may proceed to step 4052. In step4052, the cycler may begin delivery from Chamber B. After completingstep 4052, the cycler may take a measurement of the volume which wasdelivered in step 4054. This measurement may be compared to the initialfill volume measurement to determine how much of or if the entire volumewas delivered.

In the example flowchart, steps 4056, 4058, 4060, and 4062 are shown indashed outline form. These steps are optional and may not be included inall embodiments. In some embodiments, the cycler may not deliver thevolume in a chamber all at once. Instead, in some embodiments, multipledelivery and measurement steps may occur before the entire volume isdelivered from the chamber. Additionally, in some embodiments, thecycler may attempt to deliver a chamber volume multiple times in theevent that the measurement taken in 4052 is lower than desired. In suchembodiments, the cycler may operate similarly to the steps describedabove in reference to steps 4044, 4046, 4048, 4050.

After each of Chamber A and Chamber B has been emptied, the cycler mayrefill each of the chambers. The cycler may then take measurements ofthe volume of fluid that occupies each chamber. After taking thesemeasurements, the cycler may again deliver Chamber A and Chamber B asdescribed above. This process may be repeated as necessary until adesired task is complete (e.g. patient is drained to empty).

It may be advantageous to release or reduce the magnitude of anyexisting pressure in a pumping chamber of a pump cassette before avolume measurement of the pumping chamber is attempted. In anembodiment, the pump control chamber may be vented to atmosphere beforean FMS chamber volume measurement is made. In other embodiments, themagnitude of the existing pressure in the pumping chamber may be reducedwithout necessarily allowing it to reach atmospheric pressure, as longas a predetermined or prescribed level of accuracy of the FMSmeasurement can be obtained. The following description involves ventingprocedures for a two-pump cassette, but the venting procedure may beapplied equally to a pump cassette having a single pumping chamber, orone having a plurality of pumping chambers. Exemplary systems in whichthe following pump venting operations may be implemented include forexample, the peritoneal dialysis systems disclosed in U.S. Pat. Nos.5,350,357, 5,431,626, 5,438,510, 5,474,683 and 5,628,908, the contentsof which are all incorporated herein in their entireties. They may alsoinclude, for example, the hemodialysis system disclosed in U.S. Pat.Nos. 8,246,826, 8,357,298, 8,409,441 and 8,393,690, the contents ofwhich are also all incorporated herein in their entireties. They mayalso include, for example, the cardiopulmonary bypass systems disclosedin U.S. Pat. No. 8,105,265, the contents of which are also incorporatedherein in its entirety.

FIG. 186 depicts a flowchart detailing another embodiment forsynchronizing pumping operations in a two-chamber cassette.Specifically, the flowchart shown in FIG. 186 depicts a number ofexample steps that may be followed to synchronize delivery of fluid froma two-chamber pump cassette, although the scheme may readily begeneralized for use in a cassette with additional chambers (e.g. sets ofchambers ganged together such that they operate in parallel). Theflowchart depicted in FIG. 186 begins after each of Chamber A andChamber B has been filled and a measurement of the fill volumes has beentaken.

As shown, the example flowchart is similar to that depicted in FIG. 186.All of the steps from FIG. 185 are included, except that an additionalstep 4064 has been added. In this added step, the pressure in thechamber is altered to relieve the chamber of any back-pressure that mayhave developed due to, for example an occluded or partially occludedfluid line in communication with the chamber. In an embodiment, thechamber is vented. In some embodiments, the chamber may be vented to theatmosphere. In other embodiments, the chamber may be vented to apressure source which is at a pressure lower than the pressure existingin the camber during or after a delivery stroke. In alternateembodiments, the chamber may not be vented in step 4064, but rathersubjected to a negative pressure. Any other approaches to venting thepumping chamber known in the art can also be used. This may help toincrease the overall accuracy of volume measurement and fluidaccounting. Additionally, this venting may help to mitigate any possibleeffects from back pressure (e.g. due to an occluded or partiallyoccluded line). Vent steps may also be referred to herein as backpressure relief steps.

As shown in FIG. 186, the vent step 4064 occurs after Chamber A hasfinished delivering its volume and before Chamber B begins deliveringits volume. In alternate embodiments, there may be additional vent steps(not shown in FIG. 186), or the vent step 4064 may occur at a differenttime. For example, in some embodiments, the vent step 4064 may beperformed prior to each post-delivery volume measurement taken on eitherof the chambers. Alternatively, vent step 4064 may be performed prior toboth post-fill and post-delivery volume measurements taken on either ofthe chambers. Additionally, it should be noted that vent steps may beadded to any other synchronization scheme, including but not limited tothose described herein. For example, one or more vent or back pressurerelief steps may be added to the synchronization scheme depicted in FIG.184. In a specific example, a back pressure relief or venting step maybe added between each delivery and post-delivery measurement in FIG.184.

FIG. 187A depicts a flowchart detailing another embodiment forsynchronizing pumping operations in a two-chamber pump cassette.Specifically, the flowchart shown in FIG. 187A depicts a number ofexample steps that can be used to synchronize delivery of fluid from atwo-chamber pump cassette, although the scheme may readily begeneralized for use in a cassette with additional chambers (e.g. sets ofchambers ganged together such that they operating in parallel). Theflowchart depicted in FIG. 187A begins after each of Chamber A andChamber B has been filled and a measurement of the fill volumes has beentaken.

As shown, the cycler begins by delivering the volume from Chamber A instep 4070. The cycler then vents Chamber A in step 4072. After ventingChamber A, the cycler takes a measurement in step 4074 of the volumedelivered from Chamber A during step 4070. The cycler can use themeasurement from step 4074 to check that the volume in Chamber A wasfully delivered. This may, for example involve comparing the initialfill measurement with the measurement from step 4074. The cycler can usethis comparison to determine whether a predetermined amount orproportion of the fill volume was delivered. In the event that thecycler determines that the Chamber A volume was not fully delivered, thecycler can perform steps 4070, 4072, and 4074 again. These steps may berepeated until the cumulative volume from each attempt falls within apredetermined amount or proportion of the initial measurement of thevolume filled into Chamber A. As in other embodiments, the cycler (i.e.its controller) may be programmed to limit the number of retries thecycler is allowed to perform. If the limit is reached, the cyclercontroller can trigger a user alert or alarm.

After the volume in Chamber A has been delivered to the desireddestination, the cycler can begin filling of Chamber A in step 4076.After Chamber A has begun filling or after Chamber A has filled, thecycler begins to deliver Chamber B in step 4078. After Chamber B hasbeen delivered, Chamber B can be vented in step 4080. After venting, instep 4082, the cycler takes a measurement of the volume delivered fromChamber B during step 4078. The cycler uses the measurement from step4082 to check that the volume in Chamber B was fully delivered. Thismay, for example involve comparing the initial fill measurement with themeasurement from step 4082. The cycler uses this comparison to determinewhether a predetermined amount or proportion of the fill volume wasdelivered. In the event that the cycler determines that the Chamber Bvolume was not fully delivered, the cycler may perform steps 4078, 4080,and 4082 again. These steps can be repeated until the cumulative volumefrom each attempt falls within a predetermined amount or proportion ofthe initial measurement of the volume filled into Chamber B. As in theother embodiments described, the cycler (i.e. its controller) may beprogrammed to limit the number of retries the cycler is allowed toperform. If the limit is reached, the cycler controller can trigger auser alert or alarm.

After the volume in Chamber B has been delivered to the desireddestination, the cycler begins filling of Chamber B in step 4084. AfterChamber B has begun filling or after Chamber B has filled, the cyclerbegins to deliver Chamber A in step 4070. The example steps in theflowchart may repeat as necessary until a desired task is complete (e.g.patient is drained to empty).

A number of flowcharts demonstrating pumping operation processes whichinclude one or more vent or back pressure relief steps are depicted inFIGS. 186, 187A, and 189. An example graph depicting pressurizing in apump chamber during a pumping operation with a back pressure relief stepis depicted in FIG. 187B.

FIG. 187B depicts an example graph 4071 which plots pressure in acontrol chamber over a deliver stroke, back pressure relief step, andvolume measurement step. Though the graph 4071 is exemplary of any pumpchamber performing such steps in any synchronization scheme, thereference numerals for chamber A in FIG. 187A are included on the graph4071 to indicate an example deliver stroke 4070, back pressure reliefstep 4072, and volume measurement step 4074.

As shown, the delivery stroke 4070 is conducted at a positive pressure.As fluid is delivered the volume of the control chamber increases andcontroller commands the chamber to be repressurized so that its pressureremains within a desired or predetermined range. At the end of thedeliver stroke 4070, a back pressure relief step 4072 is commanded bythe cycler controller. In the example back pressure relief step 4072,the control chamber is vented toward ambient pressure. This may, forexample, be done by actuating any suitable valve or combination ofvalves in a pneumatic circuit in order to place the chamber in fluidcommunication with the atmosphere. As described elsewhere herein, inother embodiments, a back pressure relief step may involve connectingthe chamber to a venting reservoir other than the atmosphere (e.g. areservoir which is at a pressure below that of the deliver pressure ordelivery pressure range).

After the back pressure relief step 4072 is completed, the chamber maybe repressurized such that a volume measurement 4074 (e.g., via an FMSprocedure) may be made. In the example graph 4071, this volumemeasurement is made by pressurizing the chamber to a known positivepressure and then allowing it to equalize with a reference chamberhaving a known volume at a known or measured pressure. The postequalization pressure is read to determine the volume of the chamber, asdescribed elsewhere.

FIG. 188 depicts a flowchart detailing another embodiment forsynchronizing pumping operations in a two-chamber cassette.Specifically, the flowchart shown in FIG. 188 depicts a number ofexample steps that may be followed to synchronize delivery of fluid froma two-chamber pump cassette, although the scheme may readily begeneralized for use in a cassette with additional chambers (e.g. sets ofchambers ganged together such that they operating in parallel). Theflowchart depicted in FIG. 188 begins after each of Chamber A andChamber B has been filled and a measurement of the fill volumes has beentaken.

FIG. 188 depicts a synchronization scheme in which delivery from ChamberA and Chamber B can be interleaved or interlaced with one another. Asshown, one chamber may be delivering fluid while the other chamber maybe taking a volume measurement. In some embodiments, such asynchronization scheme is used if a chamber or chambers do not fullyempty during a delivery step. In other embodiments, the cycler may notbe programmed to deliver the full chamber volume in one step. Such asynchronization scheme may be used, for example, in such embodiments.

In step 4090, the cycler delivers from Chamber A. After delivering fromChamber A, in step 4092, the cycler takes a measurement of the volumedelivered from Chamber A during step 4090. As shown, at about the sametime the cycler begins to deliver from Chamber B in step 4102. Thus thecycler can interleave or interlace delivery and volume measurements. Asshown, steps 4094, 4096, 4098, and 4100 for Chamber A and steps 4104,4106, 4108, 4110, and 4112 may be similarly interleaved or interlacedwith each other. In some embodiments or in some instances a greater orlesser number of steps may be included. For example, the cycler mayperform additional interleaved steps until the full volume from thechambers has been delivered to the desired destination.

FIG. 189 depicts a flowchart detailing another embodiment forsynchronizing pumping operations in a two-chamber pump cassette.Specifically, the flowchart shown in FIG. 189 depicts a number ofexample steps that may be used to synchronize delivery of fluid from atwo-chamber cassette, although the scheme may readily be generalized foruse in a cassette with additional chambers (e.g. sets of chambers gangedtogether such that they operating in parallel). The flowchart depictedin FIG. 189 begins after each of Chamber A and Chamber B has been filledand a measurement of the fill volumes has been taken.

As shown, the example flowchart in FIG. 189 is similar to that depictedin FIG. 188. All of the steps from FIG. 189 are included, except thatadditional steps 4120, 4122, 4124, 4126, 4128, and 4130 have been added.In these added steps, the pressure in the chambers may be altered torelieve the chambers of any back-pressure (positive or negative) thatmay have developed due to, for example an occluded or partially occludedfluid line in communication with the chamber. In an embodiment, thechambers are vented. In some embodiments in which a chamber is vented,the chamber may, for example, be vented to the atmosphere, or to asource of positive or negative pressure above or below atmosphericpressure. Venting may occur for a predetermined period of time. Invarious embodiments, the predetermined period of time may notnecessarily be of sufficient duration to allow the chamber tosubstantially equalize with the venting source, be it the atmosphere, ora positive or negative pressure reservoir. In other embodiments, thechambers may be vented to a pressure source which is at a pressure lowerthan the delivery pressure. In alternate embodiments, the chamber maynot be vented, but rather subjected to a negative pressure. Any othersuitable means of venting the pumping chamber may also be used. Thisventing may help to mitigate any possible effects from back pressure(e.g. due to an occluded or partial occlusion). Additionally, this mayhelp to increase the overall accuracy of volume measurement and fluidaccounting.

As shown, the back pressure relief steps 4120, 4122, 4124, 4126, 4128,and 4130 occur before post-delivery volume measurements in the exampleembodiment. These steps are not interleaved or interlaced as are thedelivery steps and volume measurement steps. Instead, the timing ofthese steps may occur independently, in order to optimize back pressurerelief. Additionally, in some embodiments, venting steps may be includedprior to all volume measurements taken by a cycler. For example, someembodiments can include a venting step prior to volume measurementstaken to determine a volume filled during a fill step. Such additionalventing steps may, for instance, be added into any of the abovedescribed synchronization schemes. As with post-delivery venting steps,post-fill venting steps may occur independently and not be interleavedor interlaced with other steps.

In some embodiments, synchronization of pumping operations may beaccomplished by using a shared resource system and running each pumpchamber of a cassette as an independent state machine. For anindependent state machine to perform an operation, it may be required tobe in possession of an exclusive access token or resource. That is, ifone independent state machine (i.e. pump chamber) is in possession of atoken, the other chamber will be unable to also possess that token. Assoon as a chamber is finished with an operation (e.g. FMS, filling, ordelivering), the chamber may release the associated token. This willmake the token or resource available for another chamber's possession.The released token may then be possessed by another chamber as soon asanother chamber is ready to acquire it.

Using the specific example of a fill operation, a chamber independentstate machine may be required to have possession of a fill bus resourceor token. Likewise, delivery operations may require an independent statemachine to have possession of a delivery resource or token. Each of thefill and delivery buses may be treated as exclusive access resources.

Such a scheme may eliminate the need for a separate software layer whichgoverns pumping operation and pump synchronization. Instead, thefunction of this layer would be realized as an emergent behavior of thesynchronization scheme. Furthermore, such a scheme may help to increasethroughput of fluid through a pumping cassette when compared with othersynchronization schemes such as that shown in FIG. 184. This increase inthroughput may shorten the time required for a cycler to complete aprescribed fill or drain of a connected patient. As a result, thegreater throughput may help to increase the proportion of a therapyspent in the dwell phase of each cycle.

In embodiments in which a pumping cassette includes multiple pumpchambers configured to be operated in parallel, the pump chambers thatoperate in parallel with one another may be assigned to a singleindependent state machine. Additionally, in some embodiments, a non-pumpchamber independent state machine may also be included. This independentstate machine may have the capability to take possession of one or moreresources to control pumping operations.

In the above, description, the tokens are described as mutual exclusionor mutex tokens. It should, however, be appreciated that any suitablevariety of synchronizing tokens may also be used. For example, in someembodiments, semaphore tokens may be used. In such embodiments, thesemaphore tokens may be binary semaphore tokens.

FIG. 190 shows a flowchart outlining a synchronization scheme in whichpump chambers are treated as independent state machines which acquireexclusive access tokens. In the example embodiment, only two pumpchambers are included, though as would be appreciated by one skilled inthe art, such a scheme could be generalized for a pump cassette with anynumber of pump chambers. In the example flowchart, the pump chambers aresynchronizing a pumping operation generically referred to as operation“X” since any pumping operation may be synchronized in such a manner. Toperform operation “X”, a pump chamber must have possession of the busfor that operation. This possession is controlled by token “X”.

The example flowchart starts with chamber A of the pumping cassetteready to perform operation “X” and chamber B not yet ready to performoperation “X”. As shown, in step 5090 chamber A acquires token “X”.Chamber A then begins performing operation “X” in step 5092. WhileChamber A is performing operation “X”, chamber B becomes ready toperform operation “X”. Since chamber B is ready to perform operation“X”, chamber B performs step 5094 and checks for the availability oftoken “X”. Since the token is currently in held by chamber A and thetoken is treated as an exclusive access resource, chamber B will beunable to take possession of the token in order to perform the pumpingoperation. Chamber B may then repeatedly check for the availability ofthe token. Alternatively, chamber B may reserve token “X” for usage assoon as token “X” becomes available. When chamber A finishes performingoperation “X”, chamber A will release possession of token “X” in step5096. This will allow chamber B to acquire and hold the token. As shown,in step 5098 chamber B acquires token “X”. Chamber B then beginsperforming operation “X” in step 5100. In some embodiments, additionallogic may be employed before a pump chamber releases a resource ortoken. For example, in some embodiments, the controller may checkwhether the pump chamber transferred more than a predetermined amount offluid. This may help to prevent a pump chamber from releasing a token ifonly a partial stroke has been completed. Checking for partial strokesmay help to increase throughput of fluid through a pumping cassette.Additionally, checking for partial strokes may aid in air managementdepending on the embodiment.

FIG. 191 depicts an example flowchart in which the amount of fluid movedduring a pumping stroke is checked before that chamber releasespossession of a token. The flowchart depicted in FIG. 191 begins afterthe chamber has become ready to perform a specific pumping operation,operation “X”, and after the chamber has checked for the availability ofthe token for that operation. As shown, in step 5110, the chamberacquires token “X”. With token “X” in the chamber's possession, no otherchamber will be able to perform operation “X”. The chamber may thenperform operation “X” in step 5112.

A controller may then determine whether or not the pump chamber has onlyperformed a partial stroke. This may for example be done after acontroller detects the end of stroke for the pumping operation performedin step 5112. A controller may determine if a partial stroke hasoccurred by, for example, estimating the volume delivered by the chamberduring the pump stroke. In some embodiments, this may be done bymonitoring instantaneous flow rate information as the pump strokeoccurs. Such monitoring of instantaneous flow rate information isdescribed elsewhere in the specification. Alternatively or additionally,the controller may estimate the amount of stroke displacement that hasoccurred to see if a partial stroke has occurred. Such monitoring ofstroke displacement is also described elsewhere in the specification.

In the event that the estimate indicates that the stroke was not apartial stroke, the chamber may release the token it is in possession ofin step 5114. After releasing the token, the chamber may perform a poststroke FMS reading in step 5116. This reading may then be compared tothe pre-stroke FMS reading to relatively precisely determine the totalvolume delivered during the stroke.

In the event that the volume estimate does indicate that a partialstroke occurred, the token may be held by the chamber in step 5118 andthe controller can conduct an FMS measurement on that chamber in step5120. This FMS reading may be compared to a pre-stroke FMS reading todetermine if a partial stroke did in fact occur. In the event that theFMS measurement from step 5120 shows that the stroke was not a partialstroke, the chamber may release the token in step 5122. In the eventthat the FMS reading from step 5120 shows that a partial stroke didoccur, the chamber may return to step 5112 and perform the pumpingoperation again. Since the token for that operation was held, it willnot be necessary to wait for another chamber to finish the operation andrelease the token.

The cycler may repeat a pumping operation until a predetermined amountof fluid is moved or a reduced flow alert is triggered. Thepredetermined amount of fluid may, for example, be the amount of fluidexpected to be moved by a 90% stroke displacement. Alternatively, theremay be a limit on the number of retries allowed for a pumping operation.In the event that this limit is exceeded, an alert or alarm (e.g. lowflow, no flow, occlusion, etc.) may be triggered. In some embodiments,if the limit is exceeded, the token may be released by the chamber.Another chamber may then acquire the token and attempt to perform thepumping operation. If that operation also exceeds the number of allowedretries, an alert or alarm such as those described above may betriggered.

Synchronizing Pump Operations with Measurements

In some embodiments, it may be desirable to synchronize pumpingoperation of a multi-chamber cassette such that pressure changes on onechamber do not occur or are limited while another chamber is performingan FMS measurement or a specific portion of an FMS measurement (themeasurement being based on an accurate determination of pressure in thecontrol chamber of a pump). This may be desirable in embodiments inwhich there may be some transmission of pressurization activitiesbetween pumping chambers of the pumping cassette, causing perturbationsexperienced by a pressure sensor during a volume or FMS measurement whenanother pumping chamber is experiencing a large pressure swing. Byensuring pressure swings or changes on other chambers do not occur whilea chamber is undergoing an FMS measurement, any effect or disturbance onthe FMS measurement caused by the pressure swing may be avoided. Forexample, while the FMS measurement or portion of the FMS measurement isoccurring in a pumping chamber/control chamber combination, thecontroller may prohibit the other pumping chamber from performing anoperation that would entail a large pressure change (e.g. a pressurechange greater than about 7-8 kPa). For example, a pumping chamber maybe prevented from starting a pump stroke, venting, performing an FMSpre-charge, etc. while an FMS measurement is being made on anotherpumping chamber of the cassette.

In some embodiments, this may be accomplished by creating one or moretoken(s) which function similarly to the token described above inrelation to FIGS. 190 and 191. In general, a token can be viewed as anauthorization tag granted by a controller to a pump control portion ofthe controller or to a separate pump controller to perform an actionusing the designated pump. The authorization tag or token may berelinquished by the pump controller once the action is completed, theauthorization tag then being made available to the pump control portionof the controller or to a separate pump controller for assignment toanother pump. As above, the pump (i.e. comprising a pumping chamber andassociated control chamber) may be treated as an independent statemachine. These tokens may be exclusive access tokens which need to be‘possessed’ by a pump/pump chamber in order for the pump/pump chamber toperform specific operations. In one embodiment, there may be an FMStoken which, when acquired by a pump state machine, allows its pump andassociated control chamber to conduct an FMS measurement. Additionally,an FMS token may effectively prevent other pumps/pumping chambers fromacquiring a fill or deliver resource or token when a pump chamberpossesses the FMS token. (Possession by a pump/pump chamber of aresource token is meant to refer to possession of an authorization tagor token by a controller of that pump). Alternatively, when a pumpchamber state machine possesses the FMS token, other pumping chambersmay still be allowed to acquire a fill or deliver token, but may not beallowed to start its stroke right away. An FMS token may optionally beconfigured prevent other chambers from venting as well.

In other embodiments, additional tokens may be created. This may help toincrease pumping cassette fluid throughput while maintaining measurementaccuracy of the individual pumps. There may be a critical time during ameasurement (e.g., pressure measurement) of the control chamber of adiaphragm pump during which pumping operations in other diaphragm pumpson the pump cassette should be suspended. A measurement token can beassigned to or acquired by a pump in need of a measurement, and anoperations initiation token can be assigned to or acquired by any otherpump ready to perform a pumping operation (e.g., fill, deliver, vent,etc.). If there is a period of time during the measurement when anotherpump's operation may disturb the measurement, the operations initiationtoken can be temporarily preferentially assigned to or acquired by thepump possessing the measurement token during the critical time. In anembodiment, the pump undergoing measurement can acquire the operationsinitiation token at a time sufficiently ahead of the criticalmeasurement time to ensure that no other pump may initiate operations ifthe pressure changes during the operation are likely to encroach thecritical time period of the pump under measurement.

For example, in some embodiments, there may be an FMS (i.e. measurement)token and a start stroke (i.e. operations initiation) token (sometimesreferred to herein as “SS token”). In such embodiments, when the FMStoken is possessed by a pump chamber (i.e. the controller has assignedthe FMS token to the pump chamber or the state machine for the pumpchamber has acquired the token), it may prevent other chambers fromperforming an FMS measurement. When the start stroke token is possessedby a chamber, it may prevent other chambers from acquiring a fill ordeliver resource or token or prevent a stroke from starting after atoken is acquired. This may effectively stop other chambers fromstarting a stroke and experiencing the accompanying pressure change.Optionally, a start stroke token may also prevent venting of otherchambers as well.

FIG. 192 shows a flowchart outlining a number of steps which may be usedwhen a pump chamber is performing an FMS measurement. In the exampleflowchart, a FMS token and a SS token are used to aid in synchronizationof FMS measurements. As shown, in step 5130, the pump chamber finishesperforming a pumping stroke. Once the stroke has finished, the pumpchamber which finished the stroke may check to see if the FMS token isavailable in step 5132.

In the event that the FMS token is not available, the pump chamber mayproceed to step 5134. This may, for example, occur if another chamber isperforming an FMS measurement and is therefore in possession of the FMStoken. In step 5134, the pump chamber will wait for the FMS token tobecome available. If the FMS token is available or when the FMS tokenbecomes available, the pump chamber will acquire and hold the FMS tokenin step 5136. Once the chamber is in possession of the FMS token, thechamber will begin performing an FMS measurement in step 5138. Since thechamber is in possession of the FMS token, no other chamber may begin anFMS measurement at this time. Other chambers may, however, still start astroke since the start stroke token is still free.

Once the chamber reaches a predetermined point in the FMS measurementprocess, the chamber may proceed to step 5140 and acquire and hold a SStoken. This predetermined point may for example be reached apredetermined period of time after the FMS measurement process begins,or a predetermined amount of time before a critical measurement periodis reached. For example, this predetermined point may be set such thatit is a predetermined amount of time before reference and controlchamber equalization occurs. With the SS token held, other chambers maybe prohibited from starting a stroke (or, optionally, venting theircontrol chambers). As mentioned above, this may be accomplished in avariety of ways. In some embodiments, other chambers may be prohibitedfrom acquiring a new resource or token. Alternatively, chambers may beable to acquire a new token or resource, but may not be allowed to begina stroke.

In step 5142, the FMS measurement finishes. After the FMS measurementhas finished, the chamber may release the SS token and FMS token insteps 5144 and 5146 respectively. The chamber may then, in step 5147,perform a start stroke check (sometimes referred to herein as SSC) todetermine if the start stroke token is available. The start stroke checkmay, for example, be conducted by acquiring and quickly or immediatelyreleasing the start stroke token. The chamber may also check to see if aresource (e.g. the fill bus) is available at this point. In the eventthat the SS token is not available, the pump chamber will wait in step5148 for the SS token to become available. Additionally, the chamber mayalso have to wait for the desired resource or token to become available.If the SS token is available or when the SS token becomes available, thepump chamber may proceed to step 5150 and begin a stroke (assuming ithas acquired the required token).

FIG. 193 depicts an example embodiment in which FMS measurements aresynchronized using only an FMS token. As shown, the flowchart beginswith a pumping chamber finishing a stroke in step 5160. Once the strokefinishes, the pumping chamber may check to see if the FMS token isavailable 5162. If the FMS token is not available, the chamber may waitin step 5163 until the FMS token becomes available. If the FMS token isavailable, or when the FMS token becomes available, the chamber may takethe FMS token in step 5164. With the FMS token held, other chambers maybe prohibited from beginning an FMS measurement. Additionally, otherchambers may be prevented from starting a stroke. Once the FMS token isacquired by the chamber, the chamber may perform an FMS measurement instep 5166. Once the FMS measurement is completed, the FMS token may bereleased in step 5168.

In step 5170 the controller may then perform an FMS check on the chamberto determine if an FMS measurement is currently in progress. Thecontroller may also check to see if a resource (e.g. the fill bus) isavailable for the chamber at this point. In the event that the FMS tokenis not available, the pump chamber will wait in step 5172 for the FMStoken to become available. Additionally, the chamber may also have towait for the desired resource to become available. If the FMS token isavailable or when the FMS token becomes available, the pump chamber mayproceed to step 5174 and begin a stroke (assuming it has acquired therequired token).

Referring now to FIGS. 194-199, a number of example graphs show one ormore relationships between token possession and control chamberpressures of two pumping chambers over time. The bottom half of thegraphs in FIGS. 194-197 and in FIG. 199 depicts a chamber A pressuretrace 5133 and a chamber B pressure trace 5135. The top portion of eachof these graphs depicts token and/or resource possession by the twochambers. Specifically, these example graphs depict a fill bus field5180, deliver bus field 5182, FMS token field 5184, and SS token field5186 which indicates when each of these resources or tokens arepossessed by specific chambers. These graphs also have a start strokecheck (SSC) field 5188 which indicates when each pumping chamber makes astart stroke check. For exemplary purposes, the graphs shown in FIGS.194-199 are for a pumping cassette with two pumping chambers (chamber Aand chamber B). The processes shown can be generalized as well to acassette with a plurality of diaphragm pumps. To differentiate betweenthe two chambers, chamber A is assigned a light grey color and chamber Bis assigned a dark grey color in the example graphs.

Referring now primarily to FIG. 194, an example graph 5131 is depictedwhich graphically illustrates pumping synchronization using a startstroke token and a volume measurement token. The ownership status ofthese tokens is shown respectively in the SS token field 5186 and thestart stroke check field 5188. The synchronization scheme depicted inthe example graph 5131 employs a volume measurement token and startstroke token to prevent large pressure swings in other chambers (e.g.chamber B) during a critical period of a volume measurement in thechamber being measured (e.g. chamber A). The synchronization scheme issimilar to that shown and described in relation to FIG. 192. Asmentioned above, this arrangement may help to reduce any influence of alarge pressure change in another chamber on a volume measurement in thechamber undergoing measurement.

As shown, the graph 5131 begins with chamber A performing a fill stroke.During a fill stroke a control chamber (e.g. chamber A) will be atnegative pressure to draw fluid into the associated pump chamber. Thisnegative pressure is shown in the pressure trace of chamber A 5133. Asshown in the fill bus field 5180, chamber A retains control 5137 of thefill bus token for the duration of the fill stroke. This preventschamber B from beginning a fill stroke. When chamber A has completed thefill stroke 5139, the chamber may acquire the FMS or volume measurementtoken 5141, if it is available, in order to measure the amount of volumedrawn into the pumping chamber. Chamber A may also optionally releasethe fill bus token at this point. As shown in the fill bus field 5180 ofthe example graph 5131, chamber A retains the fill bus token for aperiod of time 5143 after completing the fill stroke 5139. As shown bythe pressure trace for chamber A 5133, the example period of time 5143is sufficient for the pressure of chamber A to rise from the negativefill pressure to near ambient pressure.

When chamber A releases the fill token 5145, chamber B performs a startstroke check 5149. Since the start stroke token is not possessed byanother pump chamber (see the start stroke field 5186) chamber Bacquires the fill bus token 5151. Once the fill bus token has beenacquired by chamber B, the chamber begins filling 5158 as indicated bythe chamber B pressure trace 5135. Chamber B continues to fill, retainsthe fill bus token, and is at negative pressure for the rest of theexample graph 5131.

During the volume measurement on chamber A, the chamber is brought to aknown positive pressure 5152. This may, for example, allow the chamber,once isolated, to be equalized with a reference chamber of known volumewhich is at a known pressure to determine the chamber's volume. Apressure trace for the reference chamber is not included on the examplegraph 5131 and volume measurement is described in further detailelsewhere in the specification. During the volume measurement process ofchamber A, the chamber acquires the start stroke token 5153 as shown inthe start stroke token field 5186.

As mentioned above, a start stroke token may be acquired by a chamberperforming a volume measurement such that large pressure changes inother chambers are prevented during a critical time during the volumemeasurement. In the example embodiment, the start stroke token may beacquired and held over the critical period plus a predeterminedpreceding margin period.

In some embodiments, the start stroke token may be acquired and held forclose to a latter half of the predicted time required for the volumemeasurement process. In other embodiments, the start stroke token may beacquired and held for a period of time equal to the sum of the timerequired for a chamber to equalize with the reference chamber 5154, anoptional predetermined preceding period of time 5155, and the longestexpected time 5156 required for a chamber to travel from an initialpressure to its regulation range 5157 for a stroke. The time period overwhich the start stroke token may be held by a chamber can be less thanthe time period over which the FMS or volume measurement token is held,because not all of the FMS measurement process is necessarilysusceptible to pressurization effects of nearby or adjacent chambers.This may allow for increased fluid throughput as other chambers may nothave to wait for long periods of time during volume measurements.Instead, chambers may be able to begin a stroke during a large portionof the volume measurement process for another chamber.

The equalization period 5154 may be dependent on the type of volumemeasurement operation being conducted. The equalization period 5154 may,in some embodiments, be empirically determined and preset for specificvolume measurement operations. In some embodiments, the equalizationperiod 5154 may be considered to be the critical period.

The preceding period 5155 may be a preset period of time just prior tothe equalization period 5154. In some embodiments, data collected in thepreceding period 5155 may be used in post processing to gatheradditional information about the volume measurement. For example, insome embodiments, the pressure data from the preceding period of time5155 may be post-processed to determine if the data is indicative of aleak in the system. In such embodiments, the preceding period 5155 andthe equalization period may collectively make up the critical period. Inother embodiments, the preceding period 5155 may be optional (e.g. inembodiments where a leak test is not performed) and is not included aspart of the critical period.

The longest expected time period 5156 may also be a preset period whichhas been empirically determined. The period 5156 may be the longestexpected period of time required for a chamber's pressure to change froman initial pressure (e.g. a vented or ambient/atmospheric pressure) to apressure regulation range 5157 for a pumping operation. A pressureregulation range 5157 may be a pressure range in which the controllerattempts to maintain a chamber at a set point during a pumping operationto help ensure uniform pumping flow. The pressure regulation range 5157shown in the example graph in FIG. 194 is the pressure range in whichthe controller attempts to maintain a chamber at during a fill stroke.At least a part of the longest expected time period 5156 may serve as anadded margin to the critical period.

Once the volume measurement on chamber A has completed 5159, the chamberreleases the start stroke token 5161. At this point chamber A is full offluid and ready to perform a deliver stroke. Chamber A performs a startstroke check 5165 and since the start stroke token is not owned byanother chamber (see start stroke token field 5186), chamber A acquiresthe delivery bus token 5167 and begins a deliver stroke 5169. When achamber is performing a deliver stroke, the control chamber may besubjected to a positive pressure to force fluid out of the associatedpumping chamber. This is illustrated in the pressure trace for chamber A5133 during the period (starting at about 4.3 seconds) over which thechamber is in possession of the delivery bus token (see delivery bustoken field 5182).

Referring now primarily to FIG. 195, an example graph 5171 is depictedwhich graphically illustrates pumping synchronization using a startstroke token and a volume measurement token. The ownership status ofthese tokens is shown respectively in the SS token field 5186 and thestart stroke check field 5188. The synchronization scheme depicted inthe example graph 5171 employs a volume measurement token and startstroke token to prevent large pressure swings in other chambers during acritical period of another volume measurement. Additionally, the examplesynchronization scheme illustrated in the graph 5171 uses a fill bustoken whose ownership is identified in a fill bus field 5180. Theexample graph 5171 depicts how such a synchronization scheme may operatewhen both chambers begin empty. Strokes starting from chambers in thiscondition may be referred to as initiating strokes. This scenario mayoccur, for example, when a new cassette is present in a cycler or aftera previous pumping procedure finished with all of the chambers fullydelivered.

As shown, the example graph 5171 begins with chamber A performing avolume measurement 5173. Before the volume measurement, chamber Aacquires FMS token 5175 and holds the FMS or volume measurement token.Since chamber A is in possession of the volume measurement token,chamber B must wait until the volume measurement of chamber A has beencompleted. At a point during the volume measurement of chamber A, thechamber acquires start stroke token 5176 and holds the start stroketoken. This is similar to the description above in relation to FIG. 192and FIG. 194.

When the volume measurement of chamber A is finished 5177, the chamberreleases the FMS or volume measurement token 5179 and releases the startstroke token 5181. Chamber B then acquires the FMS or volume measurementtoken 5183 and performs a volume measurement 5185. The volumemeasurement of chamber B may be conducted in the same manner as chamberA.

In the example embodiment, after a volume measurement of chamber A hasbeen made, the chamber is optionally vented 5187 toward ambient pressureor in the example embodiment to within a range of atmospheric or ambientpressure. A chamber may be vented in order to reduce the load on thepneumatic pump by leveraging atmospheric pressure to do some of the workrequired to bring the chamber pressure down toward ambient before anegative pressure stroke. As mentioned elsewhere, venting may be also beperformed after a positive pressure stroke and before an FMS measurementpre-charge in order to mitigate effects of back pressure on fluid in thechamber or on outlet valve closure, and to help increase accuracy of asubsequent volume measurement.

Once the chamber A has been optionally vented, the chamber may perform astart stroke check 5189. Although chamber B is in the process ofperforming a volume measurement, chamber B has not yet acquired thestart stroke token (see the start stroke token field 5186). As a resultthe start stroke check 5189 performed by chamber A succeeds. Chamber Aacquires the fill bus 5191 and begins a fill stroke. This is indicatedby the negative pressure of the chamber A pressure trace 5133 while thefill bus token is retained by chamber A.

Once chamber B has finished its volume measurement 5193, the chamber mayoptionally be vented 5195 similarly to chamber A. Since the fill bustoken (see fill bus token field 5180) is in possession of chamber Aafter chamber B has completed venting, chamber B is unable to acquirethe fill bus token. As a result, chamber B must wait 5197 for the fillbus token to be released by chamber A. As indicated by the chamber Bpressure trace 5135 the pressure remains constant while the chamberwaits for the fill bus token to become available. As soon as chamber Afinishes it fill stroke and releases the fill bus token, chamber B willacquire the fill bus token and begin a fill stroke.

Referring now primarily to FIG. 196, an example graph 5199 is depictedwhich graphically illustrates pumping synchronization using a startstroke token and a volume measurement token. The ownership status ofthese tokens is shown respectively in the SS token field 5186 and thestart stroke check field 5188. The synchronization scheme depicted inthe example graph 5199 employs a volume measurement token and startstroke token to prevent large pressure swings in other chambers during acritical period of another volume measurement of the pump chamber ofinterest. Additionally, the example synchronization scheme illustratedin the graph 5198 uses a fill bus token and deliver bus token whoseownership is identified respectively in a fill bus field 5180 anddeliver bus field 5182. The example graph 5198 depicts how such asynchronization scheme may operate when one chamber finishes a fill andanother chamber is ready to transition to fill. This scenario may occurseveral times throughout a pumping procedure. Similar transitionsbetween chambers performing delivery strokes may also occur. Forpurposes of example, the graph 5198 begins with chamber A performing afill stroke (as indicated by the chamber A pressure trace 5133) andchamber B empty and waiting to perform a fill stroke (as indicated forthe chamber B pressure trace 5135).

As shown, when chamber A completes a fill stroke 5201 it may acquire theFMS or volume measurement token 5203. In the example embodiment, chamberA acquires the FMS or volume measurement token 5203 prior to performingan optional vent 5205 which brings the chamber pressure to within arange of ambient pressure. As mentioned above, a vent may optionally beperformed, for instance, to minimize pump run time. As shown in the fillbus field 5180 of the example graph 5198, chamber A retains the fill bustoken for a period of time 5207 after completing the fill stroke 5201.As shown by the pressure trace for chamber A 5133, the example period oftime 5207 is sufficient for the pressure of chamber A to be vented tonear or within a range of ambient pressure. Once chamber A has beensufficiently vented, chamber A may release the fill bus token 5209. Thevolume measurement of chamber A is similar to that described above inrelation to FIG. 192 and FIG. 194

With the fill bus token released 5209 by chamber A, chamber B may thenimmediately perform a start stroke check 5211 and acquire the fill bustoken 5213. As indicated by the chamber B pressure trace 5135, chamber Bbegins filling 5215 as soon as it has acquired the fill bus token.Chamber B retains the fill bus token and continues performing a fillstroke for the remainder of the example graph 5198. Thus, in the examplesynchronization scheme, the fill bus may transition from one chamber toanother chamber as soon as it becomes available. This rapid transitionmay allow for increased fluid throughput as the amount of time when thebus is not in use by a chamber is minimized. Transitions for a deliverbus token may occur similarly. As would be appreciated by one skilled inthe art, such a synchronization scheme would similarly minimize theamount of time a delivery bus token is not in possession of a pumpchamber. This may also help to increase fluid throughput.

Once the volume measurement on chamber A has completed 5217, the chamberreleases the start stroke token 5219. At this point chamber A is full offluid and ready to perform a deliver stroke. Chamber A performs a startstroke check 5221 and since the start stroke token is not owned byanother chamber (see start stroke token field 5186), chamber A acquiresthe delivery bus token 5223 and begins a deliver stroke 5225. This isillustrated by the positive pressure of the chamber A pressure trace5133 while the chamber is in possession of the delivery bus token.Chamber A retains the deliver bus token 5223 and continues performing adelivery stroke for the remainder of the example graph 5199.

Referring now primarily to FIG. 197, an example graph 5227 is depictedwhich graphically illustrates pumping synchronization using a startstroke token and a volume measurement token. The ownership status ofthese tokens is shown respectively in the SS token field 5186 and thestart stroke check field 5188. The synchronization scheme depicted inthe example graph 5227 employs a volume measurement token and startstroke token to prevent large pressure swings in chambers during acritical period of another volume measurement. Additionally, the examplesynchronization scheme illustrated in the graph 5227 uses a fill bustoken and deliver bus token whose ownership is identified respectivelyin a fill bus field 5180 and deliver bus field 5182. The example graph5227 depicts how such a synchronization scheme may operate when apumping procedure is completed and pumping is stopped. The final strokesbefore pumping is stopped may be referred to as terminating strokes.Such a scenario may, for example, occur when a target volume has beendelivered to a pumping destination. For purposes of example, the graph5227 begins with chamber A performing a deliver stroke (as indicated bythe chamber A pressure trace 5133) and chamber B performing a fillstroke (as indicated for the chamber B pressure trace 5135). In theexample graph 5227, the controller has recognized that the target volumewill be reached during the current deliver stroke from chamber A.

As shown, when chamber B completes a fill stroke 5229 it may acquire theFMS or volume measurement token 5231. In the example embodiment, chamberB acquires the FMS or volume measurement token 5231 prior to performingan optional vent 5233 which brings the chamber pressure to within arange of ambient pressure. As shown in the fill bus field 5180 of theexample graph 5227, chamber B retains the fill bus token for a period oftime 5235 after completing the fill stroke 5229. As shown by thepressure trace for chamber B 5133, the example period of time 5235 issufficient for the pressure of chamber B to be vented to near or withina range of ambient pressure. Once chamber B has been sufficientlyvented, chamber B may release the fill bus token 5237. The volumemeasurement of chamber B may be similar to volume measurements describedabove in relation to FIG. 192 and FIG. 194. Once chamber B has finishedits volume measurement 5239 the chamber may halt pumping operations,release any tokens it possesses and wait for a controller to commandpumping to resume.

Chamber A continues its delivery stroke and retains the deliver bustoken (see delivery bus token field 5180) until the target volume hasbeen delivered to the pumping destination. In the example graph 5227, acontroller may command the delivery stroke to stop 5241 based on adelivered volume estimate maintained during the delivery strokeindicating the target volume has been reached. Such volume estimates aredescribed elsewhere herein (see. e.g. FIG. 114-121). In otherembodiments, the controller may simply allow the stroke to finish.

When the delivery volume estimate indicates the target delivery volumehas been reached the delivery stroke from a chamber may end 5243. Atthis point, the chamber may acquire the FMS token 5245 and measure theamount of volume drawn into the pumping chamber. Chamber A may alsorelease the deliver bus token at this point in some embodiments. Asshown in the delivery bus field 5182 of the example graph 5227, chamberA retains the delivery bus token for a period of time 5247 aftercompleting the delivery stroke 5243. As shown by the pressure trace forchamber A 5133, the example period of time 5247 is sufficient for thepressure of chamber A to fall to near ambient pressure. Optionally, thechamber may be vented during the period of time 5247 toward ambientpressure before being re-pressurized for a volume measurement. Althoughthis venting procedure may increase the work of the positive pressurereservoir pump, it does so for the benefit of releasing any backpressurethat may exist in the pumping chamber and its outlet valve. A volumemeasurement 5249 may then be made on chamber A and when this measurementis completed the chamber may halt pumping operations, release any tokensit possesses and wait for a controller to command pumping to resume.

Referring now primarily to FIG. 198 and FIG. 199 two example graphs 5178(FIG. 198) and 5251 (FIG. 199) are depicted. Example graph 5178 detailsthe pressures (in kPa) of pumping chambers as well as the ownershipstatus of a number of resources and tokens over a number of pumpstrokes. The number of pumping strokes include: intiating strokes(described in relation to FIG. 195) which are performed on empty pumpingchambers, delivery and fill transitions (fill transitions described inrelation to FIG. 196), and terminating strokes which are performed whena target volume is delivered (described in relation to FIG. 197).

Specifically, the example graph 5178 depicts a fill bus field 5180,deliver bus field 5182, FMS token field 5184, and SS token field 5186which indicates when each of these resources or tokens are possessed byspecific chambers. The graph 5178 also has a start stroke check field5188 which indicates when each pumping chamber makes a start strokecheck. For exemplary purposes, the graph 5178 shown in FIG. 199 is for apumping cassette with two pumping chambers; the process can begeneralized as well to a cassette with a plurality of diaphragm pumps.The pressure of pumping chamber A is shown by line 5190 in the topportion of the graph 5178. The pressure of pumping chamber B is shown byline 5192 in the bottom portion of the graph 5178. In the example graph5178, the pumping chambers are plotted pumping fluid from a heater bagto a patient. To allow for discernment between pumping chambers,elements of the graph indicating token possession by pump chamber B areshown in a heavier weight than those associated with pump chamber A.

The graph 5251 shown in FIG. 199 is the same as that shown in FIG. 198except the pressure traces (lines 5190 and 5192) are overlaid on top ofone another. The following description directly references graph 5178(FIG. 198), though the description applies to both graphs 5178 (FIG.198) and 5251 (FIG. 199). The reference signals used in graph 5251 (FIG.199) are the same as those used and described in relation to FIG. 198.

The graph or plot 5178 begins with both pump chambers empty before aninitial FMS measurement has been taken on either. This portion of theplot 5178 is indicated by the dashed box labeled “Start Pumping”. Anexample graph detailing a number of intiating strokes is described indetail in relation to FIG. 195. As shown, pump chamber A begins byperforming an FMS measurement. As shown, the chamber takes control ofthe FMS token while performing the FMS measurement. Since chamber A haspossession of the FMS token, chamber B must wait to perform an FMSmeasurement. As shown, chamber A takes possession of the SS token for aportion of the FMS measurement. In the example plot 5178, this portionincludes the equilibration period of the FMS measurement. When done,chamber A releases the FMS token which is then possessed or acquired bychamber B which performs its own FMS measurement.

While chamber B is performing FMS, but before chamber B takes possessionof the SS token, chamber A performs a start stroke check as shown in theSSC field 5188. Since the start stroke token is available, chamber Abegins a fill stroke. This fill stroke is allowed to continue after thestart stroke token is retained by chamber B. As shown in the fill busfield 5180, chamber A takes possession of the fill resource or token andretains possession of the fill bus until it finishes it fill stroke.

Once chamber B completes its FMS measurement, chamber B is ready tobegin a fill stroke. Chamber B, however, is unable to begin a fillstroke because the fill token is unavailable. Chamber B must wait untilthe fill resource is released by Chamber A to start a fill stroke as isshown in the dashed box labeled “Fill Transition”. An example filltransition is described in detail above in relation to FIG. 196. As soonas the fill bus becomes available, chamber B performs a start strokecheck, takes possession of the fill token, and begins its fill stroke.Chamber A performs an FMS measurement while this fill stroke isoccurring. After completing the FMS measurement, the chamber is ready todeliver the filled chamber volume in a delivery stroke. While chamber Bis still performing its fill stroke, chamber A does a start strokecheck, takes possession of the deliver token as shown in the deliver busfield 5182, and begins a delivery stroke.

After chamber B finishes its fill stroke and performs an FMS measure todetermine the volume filled, the chamber is ready to begin a deliverstroke. Chamber B, however, is unable to begin a deliver stroke becausethe deliver token is unavailable. Chamber B must wait until the delivertoken is released by Chamber A to start a deliver stroke. As soon as thedeliver token becomes available, chamber B performs a start strokecheck, takes possession of the deliver token, and begins its deliverystroke. This process of alternating pumping may continue as long asnecessary to move a desired volume of fluid. In some embodiments, a usermay stop or pause this process as well via interaction with the cycler(e.g. through a user interface).

As shown, the pumping synchronization scheme depicted in FIG. 198 isefficient as it helps to reduce the amount of time during which no fluidpumping is occurring. As shown in the deliver bus field 5182, after thefirst delivery stroke begins, there is relatively little time in whichthe delivery bus is not occupied delivering fluid from a pump to itsdestination. Additionally, this is accomplished while at the same timeavoiding a large pressure swing during a prescribed portion of each FMSmeasurement.

As mentioned above, once the desired volume of fluid has been moved orwhen a user pauses or stops pumping, pumping operations may cease. Inthe example plot 5178, this is shown in the dashed box labeled “StopPumping”. An example graph detailing terminating strokes of a pumpingprocedure is described in detail in relation to FIG. 197. Once thechambers finish their current pumping stroke, they perform an FMSmeasurement and do not attempt to acquire a token for the next stroke.In some embodiments, the chambers may stop pumping before their currentstroke has completed. For example, the chambers may instantaneouslyestimate volume delivered over the progression of a stroke. Once thedesired amount of volume or the target volume has been moved, FMS may beperformed and pumping operation may be stopped.

Alternatively, once the volume of fluid moved is close to the desiredvolume, a chamber may perform partial strokes after which FMS readingsare taken. For example, the chamber may be connected to a pressuresource or maintained at pumping pressure for a brief period of timebefore flow is stopped by the cycler. An FMS measurement may then beperformed. The brief period of time may be a fraction of the time whichwould be required to realize substantially full stroke displacement.Thus multiple partial strokes followed by FMS measurements may be madeuntil a target volume is reached.

Built-In Positive and Negative Pressure Reservoirs

FIG. 200 depicts an example bottom, front, left perspective view of aportion of a housing or enclosure 4200 for a device. In this embodiment,the housing portion comprises the bottom of the housing of the device.The device may be a peritoneal dialysis cycler or other dialysis machinein some embodiments. The device may be a hemodialysis machine, acardiopulmonary bypass machine or any fluid delivery machine in which apositive or negative pressure reservoir is required for variousoperations of the machine or device. The pressure reservoir can bemolded as a part of the housing of the device, providing for potentialsavings in space and allowing the device to occupy a smaller footprint,which is particularly advantageous for a portable device. As shown, thehousing portion 4200 is formed as a multi-purpose component. That is,the housing portion 4200 may not only serve as a structure to enclosecomponents of the device, but may be structured to include components orparts of components of the device. These components or portions ofcomponents may be built-in, integral parts of the housing portion 4200structure. For example, a housing portion 4200 may be formed such thatit includes or includes a portion of: pressure tanks, reservoirs orvessels, hand holds or gripping structures, various bays, compartmentsand/or component retaining features, etc.

A housing portion 4200 may be formed in any suitable manner. In specificembodiments, a housing portion 4200 may be injection molded. In suchembodiments, the mold (not shown) for the housing portion 4200 may beshaped to form each desired component or portion of each desiredcomponent included as a part of the housing portion 4200. A housingportion 4200 may also be RIM molded, compression molded, 3D printed,made with a material additive process, machined from solid stock, vacuumor pressure formed, etc. Additionally, in some embodiments, a housingportion 4200 may be constructed from structural foam such as Noryl.

As shown in the example embodiment depicted in FIG. 200, the housingportion 4200 includes a portion of a pressure reservoir 4201. Whencompletely assembled, a sealing member or sealing assembly 4203 (seeFIG. 201) may cover the portion of the pressure reservoir 4201 tocomplete the pressure reservoir 4201. In the example embodiment, thehousing portion 4200 includes a portion of a single pressure reservoir4201. In other embodiments, a housing portion 4200 may be configured toallow for any suitable number or pressure reservoirs. In variousembodiments, a housing portion 4200 may be formed such that pressurereservoirs 4201 may be disposed in any suitable location on a housingportion 4202. It may be desirable to dispose pressure reservoir 4201 ina location which accommodates any space requirements or demands relatedto other components which will be housed in the enclosure once thedevice is completely assembled.

As shown, the portion of the pressure reservoir 4201 is recessed intothe bottom face of the example housing portion 4200. In otherembodiments, a portion of a pressure reservoir 4201 may, for example, bepartially or entirely proud of a face of a housing portion 4200.Additionally, a portion of a pressure reservoir 4200 formed as part of ahousing portion 4200 may be shaped or dimensioned so as to bespace-efficient. In the example embodiment, the pressure reservoir 4201has a roughly rectangular dimension. In various embodiments, thepressure reservoir may be rounded or include more dramatically roundededges to increase the robustness of the pressure reservoir 4201structure. This may, for example, be desirable if the pressure reservoir4201 is intended to contain relatively high or low pressures, or if thepressure reservoir 4201 may be subject to physical stresses, impact, orthe like. Additionally, in some embodiments, the pressure reservoir 4201structure may be formed such that it includes one or more supportmembers such as, though not limited to a: strut, vault, buttress,counterfort, rib, or the like.

The example pressure reservoir 4201 shown in FIG. 200 includes a port4205. The port 4205 may be a void which extends all the way through thewall of the housing portion 4200. The port 4205 may allow fluidcommunication out of the pressure reservoir 4201. In variousembodiments, tubing (not shown) may be sealed (permanently or by acoupling) to the port 4205 on the top side of the housing portion 4200.Thus, the pressure reservoir 4201 may be used as a pressure source for ahydraulic or pneumatic system. Additionally, fluid may be pumped into orout of the pressure reservoir 4201 to adjust the pressure of thepressure reservoir 4201. In some embodiments, the port 4205 may be usedto both adjust the pressure of the pressure reservoir 4201 (e.g. using apump) and to provide fluid at a desired pressure to components of apneumatic or hydraulic system. In some embodiments, a pressure reservoirmay include two ports 4205. One port 4205 may be used for pressureadjustment/maintenance while the other may be used to provide fluid at adesired pressure to components of a pneumatic system. The port(s) 4205may be located so as to minimize the amount of tubing and/or routing oftubing necessary to put a pressure reservoir 4201 in communication withthe desired components of a pneumatic system. For example, in someembodiments, port(s) 4205 may be disposed such that they are spatiallyclose to or contiguous with a hydraulic or pneumatic manifold when thedevice is fully assembled.

Referring now also to FIG. 201, another bottom, front, left perspectiveof the example housing portion 4200 shown in FIG. 200 is depicted. Asshown, the housing portion 4200 is in an assembled state and a sealingmember 4203 is attached to the housing portion 4200 such that itcompletes the pressure reservoir 4201. As shown, the sealing member 4203is depicted as a cover plate in the example embodiment. The sealingmember 4203 may differ in other embodiments.

The sealing member 4203 may be attached to the housing portion 4200 inany number of suitable ways. In some embodiments, the sealing member4203 may be removably attached to the housing portion 4200 or may bepermanently attached to the housing portion 4200. In some embodiments,the sealing member 4203 may be attached using one or more suitablefasteners. In such embodiments, a gasket (not shown) may be placedbetween the sealing member and the housing portion 4200. In suchembodiments, the gasket may be any of a variety of suitable gaskets. Forexample, the gasket may be a planar gasket, form-in-place gasket, orskeletal gasket designed to follow the contact surfaces between thehousing portion and the sealing member. The gasket may comprise anelastomeric material or other compressible material suitable for forminga fluidic seal between walls of the housing portion and the sealingmember. In embodiments in which a gasket is included, the sealing member4203 may include one or more rib features which serve to retain andcompress the gasket and aid in forming a seal.

Additionally, a cooperating feature such as a recess or channel may beincluded in the housing portion 4200 which may cooperate with the one ormore ribs on the sealing member 4203. Alternatively, in someembodiments, ribs may be included on the housing portion 4200. In suchembodiments, a cooperating feature such as a groove or channel may beincluded on the sealing member. In various embodiments, o-rings may beused instead of a gasket. Making the sealing member 4203 removable maybe desirable because it may increase modularity of the device. That is,if a sealing member 4203 becomes compromised, the sealing member 4203may be removed and replaced. Thus, the entire housing portion 4200 doesnot need to be discarded. In some embodiments, the sealing member 4203may be attached to the housing portion 4200 via adhesive or glue. Insome embodiments, solvent bonding may be used. In some embodiments, thesealing member 4203 may be attached to the housing portion 4200 viaultrasonic welding. In such embodiments, it may be desirable that one orboth the materials used for the housing portion 4200 and sealing member4203 be easily ultrasonically welded. In some embodiments the sealingmember 4203 may be attached to the housing portion 4200 using vibrationwelding, hot plate welding, or laser welding. In laser weldedembodiments, the sealing member 4203 is preferably optically clear atthe wavelength of the laser to be used. The housing portion 4200 ispreferably absorbent of the wavelength of the laser. Alternatively, amaterial which is absorbent to the laser wavelength may be placedbetween the sealing member 4203 and the housing portion 4200 beforelaser welding. This material may then serve to weld the sealing member4203 and housing portion 4200 together when melted by the laser. In someembodiments, the sealing member 4203 may be overmolded to the housingportion 4200. In some embodiments, the sealing member 4203 may be snapor press fit into place on the housing portion 4200. In suchembodiments, a gasket may be used.

In some embodiments, a sealing member 4203 may be made of a materialwhich is stiff or has a high modulus of elasticity. Alternatively oradditionally, the sealing member 4203 may be suitably thick so as not todeform significantly when the pressure reservoir 4201 is at its maximumor minimum pressure. The sealing member 2403 may be constructed ofaluminum, or a reinforced plastic material. In some embodiments, thesealing member 4203 may include a clear window portion overmolded ontoan opaque portion. Alternatively, an entire sealing member 4203 may bemade of a clear material.

FIG. 202 depicts another bottom, front, left side perspective view of aspecific example of a housing portion 4200. As shown, the housingportion 4200 includes portions of a number of pressure

reservoir sections 4202 a, 4202 b. (The pressure reservoir sections 4202a and 4202 b may alternatively be denoted simply as two separatepressure reservoirs 4204 a and 4204 b in a dual pressure reservoirembodiment). In this example, a dual pressure reservoir is formed as anintegral component of the housing portion 4200, the dual pressurereservoir comprising a first section for storing positively pressurizedair, and a second section for storing negatively pressurized air, thetwo sections isolated from each other by a dividing wall 4204. In otherembodiments, the pressure reservoir sections may be configured to storeair at two different positive pressures, or air at two differentnegative pressures. In other embodiments, there may be more than twosections, each configured to store air or another gas at differentpressures, positive or negative. In the example embodiment, the pressurereservoir sections 4202 a, 4202 b are separated or segregated from oneanother by a baffle or divider 4204. In the example embodiment, thedivider 4204 is formed as an integral part of the housing portion 4200.The divider 4204 in this example is disposed such that the pressurereservoir sections 4202 a, 4202 b are of substantially equal volume andhave substantially the same overall shape, although they may be ofdifferent sizes or shapes depending on the operational requirements ofthe device for each pressure reservoir.

The divider 4204 may help in increase the strength of the walls of thepressure reservoir sections 4202 a, 4202 b. In the example embodiment,the divider 4204 is a roughly planar projection which extends in adirection generally perpendicular to the bottom face of the housingportion 2400. In other embodiments, a divider 4204 may include a curveor bend to help increase the rigidity or robustness of the pressurereservoirs. In other embodiments, a divider 4204 may help to define agreater number of pressure reservoirs. For example, in some embodiments,a divider 4204 may take the shape of an “X” or “Y”.

As shown, the example embodiment in FIG. 202 additionally includes anumber of support members or stiffeners 4206. The support members orstiffeners 4206 may be formed as an integral part of the housing portion4200. In other embodiments, a different number of support members 4206may be included. In the example embodiment, the support members 4206 aredepicted as ribs. As mentioned above, other varieties of support members4206 may be used. As shown, the support members 4206 may span from theside or perimeter walls of the pressure reservoirs 4202 a, 4202 b to thedivider 4204. In other embodiments, especially those which includesupport members 4206 which are not ribs, support members 4206 may notextend the entire distance between the side walls of the pressurereservoirs 4202 a, 4202 b and the divider 4204. The support members 4206may be substantially planar and may extend in a direction generallyperpendicular to the bottom face of the housing portion 4200. A supportmember 4206 may serve a number of functions, including, but not limitedto: increasing the rigidity of a pressure reservoir, increasing therigidity of a divider 2404, constraining a wall or a perimeter wall of apressure reservoir from bowing under pressure, and constraining a gasketfrom displacement when a pressure reservoir is under pressure. Astiffener need not be planar in shape; for example, it could bebar-shaped, extending from a side or perimeter wall of a reservoirsection to the opposing dividing wall.

In the example embodiment, the support members 4206 are structured suchthat they allow fluid communication between the volumes on opposingsides or each support member 4206. In the example embodiment, thesupport members 4206 do not extend all the way to the bottom of thedivider 4204. This may be done to ensure that the volume on each side ofeach support member 4206 is in fluid communication with the volume onthe opposing side of the support member 4206. In some embodiments, aportion of the support members 4206 may extend to and be substantiallylevel with the bottom face of the divider 2404. In other embodiments,the support members 4206 may include cutouts or pass-throughs whichallow fluid communication between volumes on opposing sides of thesupport members 4206. A lip or ledge 4208 is also shown as part of thehousing portion 4200 in the example embodiment. The ledge 4208 surroundsthe portions of pressure reservoirs 4202 a, 4202 b in the exampleembodiment. The ledge 4208 may serve as an attachment surface for asealing member. In the example embodiment a number of threaded holes areincluded in the ledge 4208. When assembled, fasteners may be threadedinto such holes to couple a sealing member to the housing portion 4200.Also a divider 4204 may include one or more threaded hole for the samepurpose. In such embodiments, and as shown, a divider 4204 may bethickened in the vicinity of such a threaded hole.

A ridge 4209 may be included along the outer perimeter of the ledge4208. The ridge projects from the housing portion 4200 in a directionthat is substantially perpendicular to the bottom face of the housingportion 4200. The ridge 4209 may serve to help locate a sealing memberduring assembly. In embodiments where a sealing member is not removable,the sealing member may be glued, bonded, welded, etc. to a surface ofthe ridge 4209. It may be desirable that a ridge 4209 have a heightwhich is substantially the same as or greater than the thickness of asealing member.

FIG. 203 depicts an assembled, bottom, front, left perspective view ofthe example housing portion 4200 shown in FIG. 202. As shown, a sealingmember 4207 has been coupled onto the housing portion 4200 via a numberof fasteners. In the example embodiment, the sealing member 4207 is acover plate. As mentioned above, in some embodiments, a gasket, o-ring,or the like may be captured between the sealing member and the housingportion 4200 to help create a seal around the pressure reservoirs.

Referring now to both FIG. 202 and FIG. 204, each pressure reservoir4202 a, 4202 b may include one or more ports 4210 a, 4210 b. The ports4210 a, 4210 b in the example embodiment are voids which extend throughthe entire thickness of the housing portion 4200. The ports 4210 a, 4210b may allow for fluid communication into and out of the pressurereservoirs 4202 a, 4202 b. In various embodiments, tubing (not shown)may be permanently sealed or reversibly coupled to the port 4205 on thetop side of the housing portion 4200. A top side view of the housingportion 4200 shown in FIGS. 202 and 203 is depicted in FIG. 205. Asshown, attachment features 4211 (e.g. nipples) may be included tofacilitate attachment of such tubing. Such features may also be formedintegral with the housing portion 4200. In the example embodiment, theattachment features 4211 are roughly cylindrical or frusto-conical. Inother embodiments, the attachment features 4211 may be barbed hollowprojections. As also shown in FIG. 205, each port 4210 a, 4210 b may beassociated with indicia indicating the chamber or reservoir 4202 a, 4202b to which it is connected. In the example embodiment a “+” and “−” areincluded to indicate positive vs. Negative pressure reservoirs. In someembodiments, the indicia could indicate “High” and “Low,” to indicate aconnection to a high pressure chamber or reservoir vs. a low pressurereservoir.

With tubing attached to the attachment features 4211, the pressurereservoirs 4202 a, 4202 b may be used as pressure sources for apneumatic or hydraulic system. Additionally, fluid may be pumped in orout of the pressure reservoirs 4202 a, 4202 b to adjust the pressure ofthe pressure reservoirs 4202 a, 4202 b. In some embodiments, the sameports 4210 a, 4210 b may be used to both adjust the pressure of eachpressure reservoir 4202 a, 4202 b (e.g. using a pump) and to providefluid at a desired pressure to components of a pneumatic or hydraulicsystem. In some embodiments, a pressure reservoir may include two ports.One port may be used for pressure adjustment/maintenance while the othermay be used to provide fluid at a desired pressure to components of apneumatic or hydraulic system. The ports 4210 a, 4210 b may be locatedso as to minimize the amount of tubing and/or routing of tubingnecessary to put a pressure reservoir 4202 a, 4202 b in communicationwith the desired components of a pneumatic system. For example, in someembodiments, ports 4210 a, 4210 b may be disposed such that they arespatially proximal to or contiguous with a pneumatic or hydraulicmanifold.

In some embodiments, other components of a device may be formed integralto a housing or housing portion 4200. As shown, in the exampleembodiment in FIG. 202, hand grips 4214 a, 4214 b are included as anintegral part of the housing portion 4200. The hand holds 4214 a, 4214 bare recessed into the bottom face of the housing portion 4200. The handholds 4214 a, 4214 b may aid in carrying the device. Additionally, oneor more storage compartments 4212 may be formed as an integral part of ahousing portion 4200. Such a storage compartment 4212 may, for examplebe used to house an on-board power source (e.g. a battery) which may beused to power the device. Referring now also to FIG. 203, a cover 4213may be coupled into place over the storage compartment 4212 to retainanything stored in the storage compartment. In some embodiments, astorage compartment 4212 may have a void 4215 (see FIG. 204) or the likewhich allows access to the interior of the device once assembled.

In reference to the top, front, right perspective view of the housingportion 4200 shown in FIG. 205, a number of additional features formedintegral with the housing portion 4200 are shown. For example, a pumpretaining feature 4220 is shown as an integral formed part of thehousing portion 4200. The pump retaining feature 4220 in the exampleembodiment is a four-walled, roughly rectangular structure which extendsfrom the top face of housing portion 4200 at an angle substantiallyperpendicular to the top face of the housing portion 4200. The pumpretaining feature 4220 may be dimensioned such that a pump component ofthe device may be stored within the retaining feature 4220. In someembodiments, the pump retaining feature 4220 may be lined with foam,elastomeric material and/or a sound damping material. This may help toreduce noise generated when running a pump component.

A manifold retaining feature 4222 is also shown in the exampleembodiment in FIG. 205. As shown, the manifold retaining feature 4222 isan integrally formed part of the housing portion 4200. The manifoldretaining feature 4222 is a four walled, roughly rectangular structurewhich extends from the top face of housing portion 4200 at an anglesubstantially perpendicular to the top face of the housing portion 4200.The manifold retaining feature 4222 may be dimensioned such that amanifold for the device may be placed within the walls of the manifoldretaining feature 4222. Also as shown, the manifold retaining feature4222 many include a number of organizer features 4224. These organizerfeatures 4224 may serve to help organize and hold in place tubing to andfrom the manifold. In the example embodiment, the organizer features4224 are recessed into the top edge of the manifold retaining feature4222.

FIG. 206 depicts a bottom perspective view of a sealing member, coverplate or lid 4230 which may be attached to a housing portion to seal thevolume of a pressure reservoir. As shown, the sealing member, coverplate or lid 4230 may include one or more support member(s) orstiffeners 4232. In the specific example embodiment in FIG. 84, thereare six support members or stiffeners 4232. In the example embodiment,the support members 4232 are depicted as ribs. As shown, there is a gapbetween support members along a medial or central plane of the sealingmember 4230. This gap may be sized such that a divider such as divider4204 of FIG. 202 may fit between the support members 4232. Inembodiments in which the cover plate is for a single pressure reservoir,such a gap need not be included. The support members 4232 may help toprovide strength or rigidity to the sealing member 4230. Additionally,the support members 4232 may constrain walls of a pressure reservoirfrom deforming when under pressure. For example, the support members4232 may prevent a side wall of a pressure reservoir from bowing in whenthe pressure reservoir is under negative pressure. In some embodiments,a support member 4232 may include at least one dovetail feature. Such afeature may for example be located along the side edge of the supportmember 4232 and may insert into a cooperating dovetail feature includedas a part of the pressure reservoir. Thus, the dovetail feature may, forexample, serve to prevent a side wall of a pressure reservoir frombowing outward when the pressure reservoir is under positive pressure.In some embodiments, the support members 4232 may be attached to thewalls of a pressure reservoir and/or divider via solvent bonding,ultrasonic, chemical or laser welds, or any other suitable means. Asshown, the support members 4232 do not extend all the way to the edgesof the sealing member 4230. This may allow the sealing member 4230 toseat on a ledge of a housing portion such as the ledge 4208 shown inFIG. 202.

Additionally, in some embodiments, support members may be included as astand-alone component which may be placed into a pressure reservoirduring assembly. In such embodiments, the support members may beattached to a surface of the pressure reservoir during assembly.

In some embodiments, it may be desirable to dispose pressure reservoirssuch that the pressure reservoirs are concentric. One, surroundedpressure reservoir may be within the footprint of another, surroundingpressure reservoir. In various embodiments, a pressure reservoir may bewithin the footprint of another, but not necessarily concentric. Thepressure reservoirs may or may not be of substantially equal volumes.Additionally, in some embodiments, the pressure reservoirs may bedimensioned differently. For example, one pressure reservoir may berelatively shallow and wide, while the other may be relatively thin anddeep, yet both reservoirs may have substantially equal volumes.

Such pressure reservoirs may be separated by a divider which fluidicallyisolates the reservoirs from one another when fully assembled. Thedivider may take the form of any variety of closed shape. A sealingmember, and in some embodiments a gasket and/or o-ring, may also be usedto seal the volumes of the pressure reservoirs. A sealing member mayalso define one or more walls of the pressure reservoirs.

Such pressure reservoirs may be pressurized to different pressures (e.g.a positive pressure and a negative pressure). The surrounding pressurereservoir may be kept at a negative pressure while the surroundedpressure reservoir may be kept at a positive pressure. Additionally, thesurface area of portion of the sealing member which is over thesurrounding pressure reservoir may be greater than that of thesurrounded pressure reservoir. Thus the negative pressure in thesurrounding pressure reservoir may serve to suction the sealing memberinto sealing relationship with the pressure reservoirs.

FIG. 207 depicts a bottom perspective view of an example embodiment of ahousing structure 4240 including portions of a number of concentricpressure reservoirs 4242, 4244. The example structure 4240 may be formedin any suitable manner known in the art. In specific embodiments, such astructure 4240 may be injection molded, be RIM molded, compressionmolded, 3D printed, made with a material additive process, machined fromsolid stock, vacuum or pressure formed, etc. Additionally, in someembodiments, the structure 4240 may be constructed from structural foamsuch as Noryl. As described above, in some embodiments, the structuremay be included as an integrally formed part of an enclosure or portionof an enclosure. When completely assembled, a sealing member or sealingassembly such as a cover plate may cover the open portions of thepressure reservoirs 4242, 4244 to completely enclose the pressurereservoirs 4242, 4244. Such a sealing member may be attached similarlyto as described above.

In the example embodiment, the pressure reservoirs 4242, 4244 areconcentrically disposed. One pressure reservoir 4244 is disposed insidethe footprint of the other of the pressure reservoir 4242. The pressurereservoirs 4242, 4244, have a roughly rectangular footprint in theexample embodiment. In other embodiments, the pressure reservoirs 4242,4244 may take any other suitable shape. In some embodiments, thepressure reservoirs 4242, 4244 may be rounded, hemispherical, etc. toadd to the robustness of the structure 4240. A plurality of pressurereservoirs may be concentrically disposed one within the other, and eachinner reservoir having a dividing wall separating it from its adjacentouter reservoir. Also in various embodiments, the pressure reservoirsmay include support members to add to the robustness of the structure4240. In embodiments including support members, the support members maybe any suitable variety or varieties of support member(s) such as, butnot limited to those described herein.

A divider 4246 is included between the two pressure reservoirs 4242,4244. The divider 4246 serves to fluidically isolate the two pressurereservoirs 4242, 4244 when the sealing member or cover plate is inplace. As shown, the divider 4246 may be a wall-like projection whichextends in a direction substantially perpendicular to the bottom face ofthe structure 4240. In the example embodiment, the divider 4246 isstadium-shaped. In other embodiments, the divider 4246 may be any otherclosed shape including, but not limited to ovoid, circular, polygonal,etc. In some embodiments, a groove 4248 may be recessed into the bottomface of the divider 4246. As shown in the example embodiment, the groove4248 is disposed at approximately the center of the bottom face of thedivider 4246. Such a groove 4248 may be sized so as to accommodate ano-ring (not shown). The o-ring may help to create a fluidic seal betweenthe pressure reservoirs 4242, 4244 when the sealing member is in place.

In other embodiments, a suitable gasket may, for example, be used inplace of an o-ring. In still other embodiments, a sealing member may bedirectly attached to the structure (e.g. via welding, adhesive, solventbonding, etc.). In such instances, a groove 4248 may not be needed.

As shown, the area of the footprint of the outer pressure reservoir 4242may be greater than the area of the inner pressure reservoir 4244. Thedepth of each pressure reservoir 4242, 4244 may be selected so as toensure that each pressure reservoir 4242, 4244 is of approximately equalvolume. In the example embodiment, since the area of the footprint ofthe inner pressure reservoir 4244 is relatively small, the innerpressure reservoir 4244 has a greater depth than pressure reservoir4242. This allows each of the pressure reservoirs 4242, 4244 to haverelatively equal volumes. This arrangement may change depending on thedifferent operational requirements the device may have for each pressurereservoir volume.

In some embodiments, one of the pressure reservoirs 4242, 4244 may beconfigured to hold positive pressure while the other is configured tohold negative pressure. In such embodiments, it may be desirable thatthe outer pressure reservoir 4242 be at the negative pressure and have alarger area footprint than the inner pressure reservoir 4244. This mayeffectively provide a suction force to a sealing member that acts tosuction the sealing member onto the structure 4240 when the device isfully assembled and pressurized. This may also serve to increase therobustness of the seals created when a sealing member is attached to thestructure 4240. In an embodiment, the surface area of the outerreservoir at the cover plate is greater than the surface area of theinner reservoir at the cover plate. Charging the outer reservoir withnegative pressure would therefore seal the cover plate against the tworeservoirs more effectively, and can provide a sealing suction uniformlyagainst the entire outer region of the cover plate, from the perimeterof the cover plate (at the perimeter wall of the outer reservoir) to thedividing wall separating the outer reservoir from the inner reservoir.If there is a desire to keep the volumes of the two reservoirs roughlyequal, the inner reservoir can be constructed to be deeper than theouter reservoir to make up for the difference in surface areas at thecover plate.

As shown, in the example embodiment in FIG. 207 a projection 4250extends into the interior volume of the inner pressure reservoir 4244.The projection 4250 in the example embodiment is substantiallycylindrical and extends in a direction which is substantiallyperpendicular to the bottom face of the structure 4240. As shown, insome embodiments, the projection 4250 may include a threaded hole. Afastener may thread into this hole to couple a sealing member to thestructure 4240. In some embodiments, the projection 4250 may include agroove 4251 recessed into the bottom face of the projection 4250. Such agroove 4248 may be sized so as to accommodate an o-ring (not shown). Theo-ring may help to create a fluidic seal around the around the fastenerwhen the sealing member is in place

A lip or ledge 4252 is also shown as part of the structure 4240 in theexample embodiment. The ledge 4252 surrounds the portions of pressurereservoirs 4242, 4244 in the example embodiment. The ledge 4252 mayserve as an attachment surface for a sealing member. In the exampleembodiment a number of threaded holes are included in the ledge 4252.When assembled, fasteners may be threaded into such holes to couple asealing member to the structure 4240. In some embodiments, a divider4246 may include one or more threaded holes for the same purpose. Insuch embodiments, a divider 4246 may thicken in the vicinity of such athreaded hole.

As shown, the ledge 4252 may also include a groove 4254. The groove 4254may be recessed into the ledge 4252 at any suitable location. In theexample embodiment, the groove 4254 is recessed into the ledge 4252proximal to the perimeter of the outer pressure reservoir 4242. Such agroove 4248 may be sized so as to accommodate an o-ring (not shown). Theo-ring may help to create a fluid seal around the outer pressurereservoir 4242 when the sealing member is in place.

Around the perimeter of the bottom of the structure 4240 may be a raisedridge 4256. In the example embodiment, the raised ridge 4256 extends ina direction substantially perpendicular to the bottom face of thestructure 4240. The ridge 4256 may serve to help locate a sealing memberduring assembly. In embodiments in which a sealing member is notremovable, the sealing member may be glued, bonded, welded, etc. to asurface of the ridge 4256. It may be desirable that a ridge 4256 have aheight which is substantially the same as or greater than the thicknessof a sealing member in some embodiments

Referring now also to FIG. 208, one or more ports 4258 a, 4258 b may beincluded for each of the pressure reservoirs 4242, 4244. The ports 4258a, 4258 b may be voids which extend through the entire thickness of thestructure 4240. Tubing (not shown) may, for example, be sealed orcoupled to the ports 4258 a, 4258 b as previously described. With thetubing attached, the pressure reservoirs 4242, 4244 may be used aspressure sources for a pneumatic or hydraulic system. Additionally,fluid may be pumped into or out of the pressure reservoirs 4242, 4244 toadjust the pressure of the pressure reservoirs 4242, 4244. In someembodiments, the same ports 4258 a, 4258 b may be used to both adjustthe pressure of each pressure reservoir 4242, 4244 (e.g. using a pump)and to provide fluid at a desired pressure to components of a pneumaticor hydraulic system. In some embodiments, a pressure reservoir mayinclude two ports. One port may be used for pressureadjustment/maintenance while the other may be used to provide fluid at adesired pressure to components of a pneumatic or hydraulic system.

FIG. 209 depicts a top perspective view of the example structure shownin FIGS. 207 and 208. As shown, the depth of the inner pressurereservoir 4244 is greater than that of the outer pressure reservoir4242. Additionally, the ports 4258 a, 4258 b are visible in FIG. 209. Asshown, attachment features 4260 may be included to facilitate attachmentof tubing. Such features may be formed integral to the structure 4240.In the example embodiment, the attachment features 4260 are roughlycylindrical or frusto-conical. In other embodiments, the attachmentfeatures 4260 may be barbed projections. As also shown in FIG. 209, eachport 4258 a, 4258 b may be associated with indicia indicating the typeof pressure associated with the pressure reservoirs 4242, 4244 withwhich the port 4258 a, 4258 b provides fluidic communication. In theexample embodiment a “+” and “−” are included to indicate positive andnegative pressure reservoirs. In some embodiments, the indicia mayindicate reservoirs having different pressurizations. FIG. 210 depicts across-sectional view of the example structure 4240 taken at line 209-209of FIG. 209. As shown, both pressure reservoirs 4242, 4244 are shown inFIG. 210. The divider 4246, and the groove 4248 in the bottom face ofthe divider 4246 are also shown, as well as the ledge 4252, the raisedridge 4256, and the groove 4254 in the ledge 4252.

Heater Bag Replenish

The heating of fluids to be delivered to a patient consumes asubstantial amount of energy. Any medical apparatus configured to infusea fluid into a patient's body cavity, or intravenously, can be equippedwith a controller that improves the efficiency of a heating deviceacting on a heater bag containing the fluid to be delivered. Althoughthe following description uses a peritoneal dialysis cycler toillustrate the system, it may be applied in a similar manner to anymedical infusion apparatus that controls the replenishment of fluid intoa heater bag, the delivery of heated fluid to a patient, the time duringwhich the fluid remains in the patient, and the withdrawal and drainingof the fluid from the patient. Regarding the infusion of dialysatesolution, it may also be advantageous in some cases to limit the amountof time the solution is kept at an elevated temperature (e.g., bodytemperature) while awaiting infusion into the patient.

There are many different types of dialysate solution which may be usedwith a dialysis machine. These solutions may for example have varyingconcentrations of osmotic agent, varying types of osmotic agents,different electrolytic components, different pH buffering components,various additives, etc. These differences between solutions may causethe solutions to act differently under various conditions. For thisreason, the cycler behavior preferably accommodates the needs of anysolution which may be used with the machine. Alternatively, a cyclercontroller can be programmed to have differing behaviors depending uponthe type of solution being used. For example, certain solution types mayhave a limited useable life once brought to a high temperature toprevent precipitation of solutes in the dialysate. The cycler behaviormay be designed to accommodate such a dialysate characteristic

As mentioned above, various embodiments of a cycler may include a heaterassembly which heats dialysate solution in a heater bag resting on theassembly prior to delivering it to the patient. The heater assembly maycomprise a heater pan or trough, sized to accept a solution bag orheater bag that has a volume which is greater than the amount ofsolution that would be delivered to a normal patient in any one filloperation. In standard practice, the heater bag is typically keptsubstantially full and the solution contained within the bag is keptwithin a defined temperature range.

In some embodiments, instead of filling substantially the entire heaterbag volume with dialysate and maintaining it at or near that full state,the heater bag may only be partially filled with dialysate. This avoidshaving a large volume of dialysate remaining heated for several fill,dwell, and drain operations. Thus, the amount of time the dialysate iskept at elevated temperature before delivery to the patient can beminimized.

For example, an amount of solution less than the volume of twoprogrammed fills may be pumped to the heater bag. This amount may bereferred to as a next cycle fill volume (e.g., volume of fill phase 758,FIG. 178). The next cycle fill volume can comprise an amount of solutionneeded to complete the next fill of the patient's peritoneal cavity. Insome embodiments, a margin or marginal volume of solution may also beadded to the next cycle fill volume. Thus the heater bag will bereplenished to a volume slightly greater than the solution volume neededto complete the next patient fill. This additional solution may helpensure that the flow rate from the heater bag during a fill of thepatient remains relatively high throughout the operation and may serveas a margin in case more solution than anticipated. The marginal volume,may for example, be a preprogrammed, fixed volume or specified as apercentage of the fill volume (or another programmed therapy volumeparameter). By replenishing the heater bag in this manner, the amount oftime the solution is held at a high temperature before being deliveredto a patient may be minimized. In an exemplary embodiment, the replenishvolume may be determined as follows:V _(R) =V _(F)+Optional Margin−V _(H)

Where V_(R) is the determined replenish volume to be transferred to theheater bag, V_(F) is the programmed next fill volume, and V_(H) is thevolume of the heater bag at the beginning of the replenish operation.

The time at which the heater bag is replenished may also be scheduled ina manner which minimizes the amount of time that its contents are keptat an elevated temperature. This may be done by replenishing the heaterbag shortly before the next fill operation is scheduled. For example,the heater bag may be refilled near the end of the dwell phase (e.g.dwell phase 756, FIG. 178) of a cycle. In some embodiments, the cyclermay determine or estimate an amount of time which will be needed toreplenish the heater bag and heat the solution for the next fill.

Heating of the transferred replenish solution can begin as soon as theheater bag replenish operation begins. The controller can be programmedto calculate an estimated heating time required to raise the temperatureof the replenished solution in the heater bag. In some embodiments, thatcalculation can be based on the temperature drop of the heater bag asthe transfer begins, and/or the volume of replenish solution to betransferred to the heater bag. The computation may, for example, includevariables such as the initial volume in the heater bag, its temperature,and the degree of temperature drop as a pre-determined volume ofreplenish fluid is transferred into the bag. Regardless of how theheating time is computed, if it is estimated by the controller to exceedthe replenish volume transfer time, the controller may command the pumpto begin the replenish operation before the remaining dwell time becomesless than the estimated time needed to bring the replenish volume to thepre-determined temperature.

Optionally, the cycler may estimate the amount of time which will beneeded for the subsequent drain operation after the current dwell. Thistime estimate may then be added to a transfer time estimate, pluspossibly an added time margin in determining how much time is availableto heat the fluid in the heater bag. The estimate may be taken intoaccount when the cycler is scheduling a replenish. For example, in someembodiments, the replenish may begin when it is determined that acalculated amount of time before the start of the current cycle's drainremains. This amount of time may be calculated as follows:Time Before Drain (replenish start time)=Optional Margin+ReplenishVolume Transfer Time+(if greater than zero (Replenish Volume HeatingTime−Drain Time))

Optionally, the controller may compute the contribution that thesubsequent drain phase will provide to raise the heater bag fluid to itstarget temperature (e.g., drain phase 754, FIG. 178). This will allowthe controller to initiate heater bag filling later during the dwellphase (e.g., dwell phase 756) by the amount of time available tocontinue to heat the fluid during the drain phase (e.g. drain phase754). In some embodiments, at least one estimated amount of time (e.g.the replenish/fluid transfer time or heating time) may be inclusive ofan added time margin to help ensure that the solution is not less thanthe programmed temperature by the start of the next cycle. This may helpto ensure that a drain is not postponed due to volume transfer in areplenish taking longer than anticipated.

Alternatively, the total volume of the heater bag may be relativelysmall (e.g. no larger than the volume of about one and a half fills).This may help to ensure that solution in the heater bag is notmaintained at high temperature for excessively long periods of time.Instead, the solution in the heater bag will be used over a small numberof cycles (e.g. two cycles). In such embodiments, there may be multiplesets available to a user, each of which having differing heater bagsizes. This may allow for a user to perform a therapy with a heater bagwhich is appropriate for their prescribed fill. In some embodiments,sets with heater bags made of varying materials may also be madeavailable. For example, there may be sets with heater bags which aresubstantially impermeable to gases such as carbon dioxide.

FIG. 211 shows a flowchart outlining number of example steps which maybe used to replenish a heater bag with dialysate solution. The stepsshown in FIG. 211 help to minimize the amount of time which the solutionis heated in the heater bag before delivery to the patient. Theflowchart begins after the heater bag has been initially filled andheated at the start of the therapy. As shown, in step 4900 the cyclerfills a patient's peritoneal cavity with solution from the heater bag.This may substantially deplete the heater bag to near empty. The dwellphase of the cycle may then begin. The cycler controller monitors theremaining dwell time to ensure that the remaining dwell time is greaterthan or equal to the time needed to replenish the heater bag and heatsolution for the next fill. When the remaining dwell time no longerexceeds the time needed to replenish the heater bag and heat solutionfor the next fill, step 4904 may be performed. Alternatively, the cyclermay schedule the replenish such that there will be enough time toreplenish the heater bag and heat the solution. The cycler controllerthen waits until the scheduled time and proceeds to step 4904.

In step 4904, the cycler replenishes the heater bag with the volumeneeded for the next fill operation. As mentioned above, the cycler mayfill the heater bag to a volume that is greater than is required for thenext fill. For example, the heater bag may be filled to the volumeneeded for the next fill plus an additional marginal volume of 10-25% ofthe fill volume. The cycler may also begin to heat the solution pumpedto the heater bag in the replenish period to within a pre-determinedrange of a pre-determined temperature set point. This temperature setpoint may be fixed or programmable by a user, or by a clinicianauthorized to alter the prescription parameters and settings of theperitoneal dialysis cycler.

After the time allotted for the dwell phase elapses, the cycler proceedsto step 4906 and begins to drain the patient. Optionally, heating of thesolution up to within the range of the temperature set point maycontinue as step 4906 is performed. After the drain operation completes,the cycler returns to step 4900 and refill the patient with solutionfrom the heater bag. If the solution is not within the range of thetemperature set point, the cycler may instead continue to heat thesolution in step 4908 until the solution is within a range of thedesired temperature set point. This will help to ensure that solutionsignificantly above or below the desired temperature is not delivered toa patient.

Solution Expiration Timers

In some embodiments, a cycler may be programmed to determine a solutionset up or staged for use in a dialysis therapy has expired.Additionally, a cycler may be programmed to notify a user when asolution has expired. The cycler controller may disallow use of theexpired solution and in some embodiments, may require the user toterminate or abort a therapy such that a new therapy with fresh solutionmay be set up. This may for example be desirable in cyclers in whichvery long therapies (e.g. up to 48 hours) may be programmed, or incyclers which allow a user to pause a therapy for long periods of time.

In some embodiments, a cycler may have one or more solution expirationtimers that start or may be triggered to start at a predefined point inthe therapy. Each of the solution expiration timers may be used for adifferent solution reservoir. For example, a first solution expirationtimer may be used for a first solution reservoir and a second solutionexpiration timer may be used for a second solution reservoir. The firstsolution expiration timer may be triggered to start at a firstpredefined point and the second solution expiration timer may betriggered to start at a second predefined point. A single solutionexpiration timer may also be used for a number solution reservoirscontaining the same type of dialysate solution. A solution expirationtimer may allot a predetermined period of time for the therapy to makeuse of the solution. The predetermined amount of time may vary dependingon the type of solution being used. If there are multiple solutionexpiration timers, the predetermined amount of time may differ for eachtimer. If the therapy does not use the solution before the time elapses,the solution may be deemed expired by the cycler and treatedaccordingly. If there are multiple solution expiration timers withdifferent allotted periods of time, one solution expiration timerexpiring may cause one or more other solution expiration timer to alsoexpire.

In some embodiments, the amount of time allotted for a solutionexpiration timer may vary by temperature of the solution. Solutionstored in a staged solution bag may be subject to a first solutionexpiration timer and may then be subject to a different solutionexpiration timer after being transferred into a heater bag. Inembodiments in which a cycler heats the solution to a temperature setpoint defined by the user or a prescriber, the system controller maycompute an expiration time for that solution expiration timer based onthe value of the temperature set point.

In some embodiments, two solution expiration timers may be used. Onesolution expiration timer may be for a set of staged solution bags andanother solution expiration timer may be for the heater bag. Thesolution bag expiration timer may be programmed to begin when the cyclercontroller determines that the solution bags have been connected to theset. The heater bag expiration timer may begin each time the heater bagis depleted to a residual volume before it is refilled with freshsolution. For example, in embodiments which schedule replenishes asdescribed above in relation to FIG. 211, the timer may restart at everyreplenish of the heater bag.

In various embodiments, one or more solution expiration times may beestablished for each type of dialysate compatible for use with thecycler. The cycler controller may determine which type of solution isprogrammed for use with the therapy. Information about the solution usedfor the therapy may also be read from a barcode or the like on asolution line or may be input by the user via a user interface of thecycler. The predetermined period of time allotted for the solutionexpiration timer may be chosen to match a dialysate solution to be usedin the therapy. For example, the cycler controller may match thedetermined solution type to a predetermined period of time programmedfor that solution in a look-up table. If more than one type of solutionis to be used for the therapy, the solution with the shortest expirationtime may be used to set the predetermined period of time allotted forthe solution expiration timer. Multiple solution expiration timers mayalso be set up so that there is one timer for each of the differentsolution types used during the therapy.

Alternatively, the one or more solution expiration timer may not besolution specific. In such embodiments, this solution expiration timermay be set such that it would be appropriate for the solution which hasthe shortest expiration time. The solution expiration times for varioussolutions may be determined based upon manufacturer recommended values.

If a solution bag expires, the cycler may, for example, no longer drawfluid from that solution bag. The therapy may be allowed to continue ifother solution bags connected to the set have not yet expired.Additionally, in some embodiments, the user interface of the cycler maynotify a user of the solution bag's expiration. In such embodiments, theuser may have the option of replacing the solution bag.

Alternatively, there may only be a single solution bag expiration timerfor all of the solution bags attached to the set. In the event that thetimer expires, the user may be required to abort the current therapy andbegin a new therapy with fresh supplies. If the solution bag expirationtimer expires, it may also cause the heater bag expiration timer toexpire.

If the heater bag expires, the cycler controller may be programmed tonot deliver the solution in the heater bag to the user. The cycler may,for example, pump all of the solution in the heater bag to the drainline to discard the solution. The heater bag may then be refilled andthe heater bag expiration timer may be restarted. The user may benotified of the heater bag's expiration. Alternatively, if there is notenough solution to refill the heater bag, the user may be required toabort the current therapy and begin a new therapy with fresh supplies.In some embodiments, any remaining solution may be delivered to theheater bag and heated. This solution may then be delivered to thepatient so that it may dwell in the patient while new supplies aregathered. This may help to minimize loss of therapy.

FIG. 212 shows a flowchart outlining a number of example steps which maybe employed by a cycler using solution expiration timers. In the exampleflowchart, the cycler has a solution bag expiration timer and a heaterbag expiration timer. As shown, in step 4920 the cycler determines thatsolution bags have been connected to the set. The cycler may then, instep 4922, begin a solution bag expiration timer. The cycler may thenfill the heater bag in step 4924. After the heater bag has been filled,the cycler may start the heater bag expiration timer in step 4926.

In step 4928, the therapy is performed. If during the therapy, theheater bag is emptied and replenished, the heater bag expiration timermay be reset in step 4930. Otherwise, if the therapy concludes beforeany expiration timers elapse, the therapy may be completed normally. Ifan expiration timer elapses before the therapy concludes, the cycler mayindicate that the solution has expired in step 4932. If it is the heaterbag expiration timer that has expired and there is sufficient solutionin the solution bags, the cycler may discard the solution in the heaterbag and replenish it with solution from the solution bags in step 4934.If there is not enough solution to replenish the heater bag, the cyclermay proceed to step 4936 and instruct the user to abort the therapy andstart a new therapy with fresh supplies. The cycler may also proceed tostep 4936 if it is the solution bag expiration timer that has expired.

FIG. 213 depicts an example screen 5610 which may be generated by aprocessor for display on a user interface of a cycler. The examplescreen 5610 indicates to the user that a solution expiration timer hasexpired. Such a screen may for example be displayed in step 4932 of FIG.212. In the example embodiment, the solution expiration timer which hasexpired is the heater bag solution timer.

As shown, the example screen 5610 includes an alert 5612 which declaresthat solution has expired and provides an error code. The screen 5610also includes text which informs the user how to resolve the problem. Inthe example screen 5610, the text instructs the user to postpone a fillphase so that the heater bag solution may be discarded and replaced. Auser may be required to navigate to another screen on which they confirmor elect to replace the solution in the heater bag. In the exampleembodiment, such a screen may be navigated to by interacting with atreatment options button 5614 on the screen 5610. In some embodiments, aresume button 5516 on the screen 5610 may be disabled until a user hasreplaced the solution.

Also shown on the example screen 5610 is a time notification 5518. Thetime notification 5518 may inform the user when a solution timer isgoing to expire. The time notification 5518 may be triggered for displaywhen a predetermined amount of time before a solution expiration timerexpires is remaining. In some embodiments, for example, in embodimentswhere a user may disconnect from a cycler during a therapy, the timenotification 5518 may inform a user when they must reconnect andcontinue the therapy to avoid a solution timer from expiring. In theexample embodiment, the time notification 5518 is a reconnect by timewhich informs the user that they had to reconnect by 7:55 PM to avoidthe heater bag expiration timer from expiring. As shown by the clock5620, the reconnect by time passed 3 minutes ago.

Flow Check

When draining solution from the peritoneal cavity of a patient it is notunusual for a patient to perceive an uncomfortable tugging sensation.Additionally, this tugging sensation may be more prone to occur when theperitoneal cavity is empty or nearly empty. For this reason, it may bedesirable for a cycler to perform a flow check to ensure that thepatient is carrying fluid that needs to be removed. Such a flow checkmay for example be performed before all drains or may be performed priorto certain types of drains. For example, since discomfort is more oftenreported during initial drains, flow checks may be made before aninitial drain is performed by the cycler. The flow check may gentlyattempt to remove fluid from a patient until the controller determineswhether or not there is any fluid volume in the patient's peritonealcavity that requires draining. The cycler may, for example, check to seeif a flow rate above a predetermined threshold value can be reached, asthis would suggest there is indeed fluid in the patient that should beremoved. This may help to minimize or prevent a perceived tuggingsensation when there is relatively little fluid, or an insufficientamount of fluid to be drained. The cycler controller may set the pumpingpressure for the drain based on the flow rate determined during the flowcheck. A flow rate above a preset threshold may allow the drain toproceed using a greater force (greater negative pressure).

In prior devices, instead of performing a flow check, the cyclercontroller would attempt to pull fluid from the peritoneal cavity at astandard or nominal preset pressure. The cycler would be programmed tocontinue the drain phase until a minimum elapsed drain time or a minimumdrain volume was reached. If the resulting flow rate were below a giventhreshold (e.g. 15 ml/min. over a 45 second period), the cycler wouldattempt to push fluid back to verify that there was no line occlusion.If no line occlusion was detected, pumping could resume at a lowerpressure. If flow remained below a threshold value for another period oftime (e.g. 300 seconds), the cycler would either alert the user or allowthe user to bypass the remainder of the drain phase. This procedure insome cases could result in episodes of patient discomfort, which now canbe mitigated by the flow check procedure.

In some embodiments, a cycler may perform a flow check by attempting topull fluid from a patient at a flow check pressure. The flow checkpressure may be selected so that it is more positive (i.e. closer toatmospheric) than that used during a normal drain operation. Forexample, the difference between the flow check pressure and the normaldrain pressure may be between approximately 2 kPa and 6 kPa. In oneexample, a flow check pressure may be set at about −6.5 kPa while normaldrain pressure may be set at about −9.5 kPa. Other pressure values maybe used. The selected pressures may be nominal values that can deviateby a pre-determined margin from the selected pressure while a pumpingoperation at that pressure is being performed. Additionally, in someembodiments, different flow check pressures may be used for differentdrains. For example, the flow check pressure used during an initialdrain may be weaker (i.e., less negative pressure) than that used duringa mid-therapy drain. Selecting the flow check pressure so that itcreates a weaker vacuum than the normal draining pressure may feelgentler to the patient. In some embodiments, a user or a clinician maybe have the option of setting the flow check pressure.

FIGS. 214A and 214B show a flowchart of a cycler performing an initialdrain that starts with a flow check. As mentioned above, flow checks maybe performed on other drains during a therapy as well. As shown, thedrain starts in step 5530. As shown in step 5532, the drain begins witha flow check at a first pressure which is a flow check pressure. In theexample embodiment, the drain begins with a drain pressure of −6.5 kPa.

In the event that the flow rate during the flow check is determined tobe greater than a flow rate threshold, the cycler may check to see thata flow rate above the threshold is maintained for a predetermined periodof time (e.g. 30 seconds). The flow rate threshold may, for example, bea value between approximately 35 ml/min and 75 ml/min. In an embodiment,the flow rate threshold may be approximately 50 ml/min.

If the flow rate is maintained above the threshold, the cyclercontroller may set the drain pressure to a second pressure considered tobe a normal drain pressure in step 5544. This pressure is generallygreater (i.e. more negative) than the flow check pressure. In theexample embodiment, the normal drain pressure is shown as −9.5 kPa. Theflow rate during the drain may continue to be monitored to determine ifthe flow rate decreases below the flow rate threshold.

In the event that flow rate during the flow check or a drain at normalpressure is determined to be less than or equal to the flow ratethreshold, the pressure for the drain operation may be set to a reducedflow pressure in step 5534. In the example embodiment, the reduced flowpressure is the same as the flow check pressure, though this need notalways be the case. If the reduced flow condition persists for apredetermined period of time (e.g. 30 seconds), a reduced flow alert maybe signaled to a user in step 5536. In some embodiments, this alert maybe a silent alert and be displayed as a text notification on the userinterface of the cycler.

In the event that the flow rate is less than the no flow rate, in someembodiments a push back attempt may be performed in step 5538. In a pushback attempt, a cycler may attempt to pump a small volume of fluid intothe patient's peritoneal cavity. This may allow the cycler controller todetermine if the line is occluded, as the cycler will be unable todeliver the fluid if an occlusion is present. If a low flow condition isrelated to a peritoneal catheter tip being lodged against a surface orin a tissue recess, the push-back of a small amount of fluid may besufficient to disengage the catheter tip. The low flow condition maythus be relieved without the cycler controller necessarily having tonotify the user. The controller in this case may re-attempt a flow checkprocedure. In some embodiments, step 5538 may only be performed if theflow rate has been below the low flow rate for a defined period of time(e.g. 30 seconds). In the event that the pushback attempt in step 5538fails, the cycler may notify the user that an occlusion exists in step5540. The drain may then be paused in step 5542 and a user may have theoption of continuing or bypassing the drain. If a user elects tocontinue the drain, another flow check may be performed in step 5532 andthe flowchart may start over.

If a pushback attempt is successful, or a pushback attempt isunnecessary because the flow rate is greater than the no flow threshold,the cycler may check to see if a minimum drain time has expired orelapsed. This time may, for example, be a clinician programmableparameter. If the minimum drain time has not elapsed, the cycler maycontinue to monitor the flow rate returning to step 5534 or step 5544 toset the drain pressure accordingly.

If the minimum drain time has expired, the cycler may check to determineif the flow rate has been below or equal to the flow rate threshold forgreater than a predetermined period of time. This period of time mayalso be modifiable by a user such as a clinician. In the exampleembodiment, the period of time is shown as 150 seconds.

In the event that the flow rate has been at or below the flow ratethreshold for more than the predetermined period of time, a reduced flowalert may be signaled to the user in step 5546. This alert may include atext notification displayed on the user interface of a cycler and may beaccompanied by an audible noise or tone. If the flow rate persists at orbelow the flow rate threshold, another reduced flow alert may besignaled to the user in step 5548. This alert may be a higher levelalert than that signaled in step 5546. The drain may then be paused instep 5542 and the user may elect to bypass or continue the drain asdescribed above.

In the event that the flow rate is above or rises above the flow ratethreshold either before or after step 5546 is to be performed, a cyclercontroller may check to determine if a minimum pre-determined drainvolume has been drained from the patient. If the minimum drain volumehas not been met, the cycler may continue to monitor the flow ratereturning to step 5534 or step 5544 to set the drain pressureaccordingly. If the minimum drain volume has been met the cycler maycheck to determine if the flow rate is above the no flow rate. If theflow rate is above the no flow rate, the cycler may end the drain andproceed to the next phase of a cycle in step 5550. Since the exampleflowchart shown in FIGS. 214A and 214B applies to an initial drain, theintraperitoneal volume of the patient may be set to zero in step 5550 aswell. In embodiments in which similar logic is used in other therapydrains, the patient volume may not be reset to zero after the drain. Inalternative embodiments, if the minimum drain volume has been drainedfrom the patient, the cycler may proceed directly to step 5550.

If the flow rate is determined to be below the no flow rate after theminimum drain volume has been drained from the patient, a cyclercontroller may command the cycler to perform a pushback in step 5552. Insome embodiments, this pushback back may not necessarily be performed.For example, in some embodiments, if a pushback was performed in step5544, a pushback may not be performed in step 5552. If the pushback issuccessful, the cycler may end the drain and proceed to the next phaseof a cycle in step 5550. If the pushback attempt is unsuccessful, anocclusion alert may be signaled to a user in step 5554. The drain maythen be paused in step 5542. A user may then elect to bypass the drain,attempt to resolve the problem and continue with the drain as describedabove.

In some embodiments, a cycler may be configured to perform either normaldrains or soft drains. This may be selectable by a user or caregiver viathe user interface of the cycler. A processor or controller of thecycler may generate a screen for display on the user interface whichallows the user to alter the pumping pressure from a first pumpingpressure (e.g. normal pumping pressure) to a second pumping pressure(e.g. soft pumping pressure or weaker pumping pressure). This screenpreferably is presented to the user during a drain. The pumping pressureoptionally may only be altered for the pumping chamber fill stroke. Inresponse to the user changing the pumping pressure via the userinterface, the processor may control the pneumatic circuit of the cyclerto apply a different pumping pressure to the pumping chambers of aninstalled cassette.

In some embodiments, this feature may be enabled or disabled by aclinician. For example, a clinician may enable such an option for apatient who reports tugging or discomfort during drains. In variousembodiments, this option may only be enabled for certain types ofdrains. For example, a clinician may have the ability to allow the userto perform soft drains during initial drain.

Such an option may allow the user to switch to a gentler drain in theevent that a drain at normal drain pressure is causing discomfort. If anoption to select a soft drain or normal drain is available, the cyclershould preferably default to performing a normal drain as soft drainsmay shorten the dwell times for a therapy. The option may, for example,only be made available after a reduced flow condition is detected by thecycler controller. In other embodiments, the user may have an option ofselecting between normal drains and soft drains when starting thetherapy. In some embodiments, the user may be able to specify specificdrains as soft drains and other drains as normal drains.

A soft drain may be at a weaker pressure than that of the normal drain,and may be pre-set or may be user-definable via the user interface. Thesoft drain may, in some embodiments, use a pumping pressure similar tothe pumping pressure used during a flow check or may use the pressureset point defined for the flow check. The soft drain pumping pressuremay for example, be weaker than the normal drain pumping pressure bybetween about 2 and 6 kPa. In some embodiments, a user such as aclinician may define the pressure set points for the normal drain andsoft drain. Alternatively, the reduced pumping pressure may be selectedfrom a range of pumping pressures. Optionally, a clinician may beallowed to create another drain profile. For example, a clinician maydefine a normal drain, softer drain, and softest drain pressure. Theuser may have the ability to select any of these pre-defined drain typesif desired. If a user has set a maximum therapy time for a course oftherapy, the controller may not modify the drain pressure unless areduced flow condition has been detected.

FIG. 215 depicts an example user interface screen which may be displayedon the user interface of a cycler during a drain. Specifically, thescreen shown in FIG. 215 is an initial drain screen 5000. As shown, theinitial drain screen 5000 includes a variety of information about thedrain and the therapy. As shown, the screen also includes a switch tosoft drain option 5002. The switch to soft drain option 5002 may, insome embodiments, be selected at any time during the drain. In otherembodiments, the switch to soft drain option 5002 may not be enabled ormay be grayed out until after a user presses a pause button 5004 topause the drain. This may help to avoid an accidental button press ofthe switch to soft drain option 5002 which would slow down the drainoperation for no need. In other embodiments, the switch to soft drainoption 5002 may not be present on all drain screens. Instead, a user mayneed to navigate to a switch to soft drain option 5002 by selecting amenu option 5006 on the user interface. When the soft drain option 5002is selected and the drain pressure is dropped to the soft drainpressure, the user interface may similarly be used to return to a normaldrain if desired. As would be appreciated by one skilled in the art,other embodiments may have options for multiple different types ofdrains such as, e.g., a normal drain, softer drain, and softest drain.In some embodiments, instead of providing a button, the switch to softdrain option 5002 may be implemented in the form of a slider bar. Oneend of the bar may be the weakest pressure which may be defined for useduring a drain. The other end of the bar may be the normal drainpressure. The user may select a desired pressure from anywhere in therange of pressures between each end of the bar. Optionally, thecontroller may compute the effect on therapy time, pumping time oranother measure of the lengthening or shortening the time needed todrain a volume of fluid in response to a change in the pumping pressure,and display information on this effect on the user interface. In anembodiment, the user may be required to confirm on the user interfacethat a change in pumping pressure is still desired.

The triggering flow rate or the time duration at that lower flow ratemay vary, depending on patient-related or clinician-related factors.Additionally, the amount of time which the cycler continues pumping atlower pressure may vary. In some embodiments, pumping pressure may beadjusted based upon flow rate at any point in a therapy. For example, inthe event that a reduced flow rate is determined to exist, the pumpingpressure may be lowered to minimize patient discomfort. Such a reducedflow rate condition may, for example, be a low flow condition of, e.g.50 mL/min. There may be multiple pumping pressures assigned to a varietyof flow conditions. For example, there may be a “normal” pumpingpressure which is used in normal flow conditions (e.g. flow greater than50 mL/min). There may be a low flow pressure for flow conditions whichare less than the normal flow condition flow rate. There may also be ano flow pumping pressure which may be used in the event that the flowrate is very low (e.g. less than or equal to 15 mL/min).

Pumping pressure need not be assigned based on discretely defined flowconditions (e.g. normal flow, low flow, no flow). Instead, in suchembodiments, pumping pressure may be adjusted on a gradient. That is,the pumping pressure may increase or decrease in magnitude in arelatively continuous manner relative to flow rate. The gradient may belinear or non-linear. For example, the magnitude of the increase inpressure may be proportional to the magnitude of the increase in flowrate and the magnitude of the decrease in pressure may be proportionalto the magnitude of the decrease in flow rate. The pumping pressure maybe adjusted in a substantially continuous fashion as flow rate databecomes available. This continuous adjustment may occur after eachstroke or may occur as each stroke progresses if flow rate is estimatedduring the progression of the stroke. The controller may be programmedto limit the pump pressure variation to within a pre-determined range ofpressures. In embodiments in which the pumping pressure used increasesor decreases in magnitude relative to the flow rate, a drain operationmay still begin with a flow check. That is, the drain operation maystart with the negative pressure for the drain phase being set at aninitial flow check pressure for a predetermined period of time. Thispressure may be selected so that it would be appropriate for a reducedflow condition (e.g. −6.5 kPa) in order to minimize any tuggingsensation experienced by the user at the start of the drain operation.If the flow rate falls below a predefined threshold for more than apredetermined period of time, the cycler controller may stop adjustmentof the pumping pressure. If the total volume drained during the drainoperation is less than the target volume for the drain, a pushback maybe performed to check for an occlusion. If the total volume drained hasat least reached the target volume for the drain operation then thecycler controller may determine that the drain operation has completedand move onto the next phase of the therapy.

In some embodiments there may be a plurality of different pressures foreach defined flow condition. These different pressures may be assignedbased upon the source and the destination for the fluid being movedduring the pumping stroke. For example, a first pumping pressure may beused when fluid is being filled into a patient's peritoneal cavity at adefined flow rate or flow rate range. A second pressure may be used whenfluid is being drained from the patient at a defined flow rate or flowrate range. A third pressure (e.g., closer to the maximal availablepressure from the pressure reservoirs) may be selected if no fluid isbeing pumped to or from a patient (e.g. chamber to drain, chamber toheater bag, heater bag to chamber, etc.), in which case there may be noneed to alter the pressure based upon flow rate.

Automated Effluent Sampling

In some embodiments, when programming a therapy, a user may be able toenable/disable or turn on/off an automated sampling parameter. Theautomated sampling parameter causes a cycler to automatically fill aneffluent sampling bag with spent dialysate from a patient during thetherapy. The user may be able to define a number of additionalparameters which may be used to specify various aspects of the automatedsample taken. For example, these additional parameters may be used todefine a sample volume to be taken, and when in the therapy a sample isto be taken. They may also be used to define how many samples are to betaken or how many sample bags are to be filled. In some embodiments,these additional parameters may only be enabled or unlocked for editingif the automating sampling parameter has been enabled. In someembodiments, there may be a variety of pre-set sampling regimens withdefinable parameters from which a user may choose. For example, asampling regimen may include parameters appropriate for a peritonitistest. A sampling regimen may also include parameters which would beappropriate for a peritoneal equilibration test or peritoneal membranetransport function test.

In one embodiment, an effluent sampling reservoir may be placed intofluid communication with a set installed in the cycler. The cycler maypump spent fluid from the connected patient into the effluent samplingreservoir as prescribed by the therapy program. In various embodiments,the user may be asked to identify a fluid port of the dialysis set towhich the effluent sampling reservoir has been connected or may bedirected to attach the reservoir to a specific port. Alternatively, aset intended to be used in therapies with automated effluent samplingmay be provided. In such embodiments, the effluent sampling reservoirmay be attached to a specific port on the dialysis set and the cyclercontroller may command pumping to that port when performing an automatedsampling operation. In some embodiments a set may include a connectorfor an automated sampling reservoir which is unique to the automatedsampling reservoir and may only couple to a corresponding unique matingconnector on an automated sampling reservoir.

In other embodiments, a feature of a set or fluid line installed in acycler may be used to determine that the cycler is to take an automatedeffluent sample. In such embodiments, the feature may, for example be aspecific geometry which is sensed by one or more sensors in a cycler.When a cycler controller receives data from a sensor indicating that thespecific geometry is present, the controller may command the cycler topump fluid to an effluent sampling reservoir during the therapy. In someembodiments, there may be multiple different geometries which may bedetectable by the sensor(s). Each geometry may correspond to effluentsample programs with different sampling parameters. The sensor(s) may beany suitable sensor or combination of sensors, such as, but not limitedto a contact sensor (e.g. microswitch),

Alternatively, the feature of the set or fluid line may be a magnet ormagnetic feature included as part of the cassette or fluid line. Wheninstalled in the cycler, a hall effect sensor in the cycler may detectthe presence of the magnet or magnetic feature. When a cycler controllerreceives data from the hall effect sensor indicating the magnet ormagnetic feature is present, the controller may command the cycler topump fluid to an effluent reservoir during the therapy.

In another embodiment, a cycler may use an optical sensor to read ordecode an identifying mark on a set or a fluid line installed in acycler. The identifying mark may include a code interpretable by thecontroller that an automated effluent sample is to be taken during atherapy. Additionally, the identifying mark may further be coded tospecify various parameters relating to the effluent sample to be takenduring the therapy. Such an identifying mark may comprise indicia suchas, but not limited to 2-D indicia (e.g. a barcode, data matrix, etc.),or any other suitable indicia. In some embodiments, the indicia may beincluded on an identification tag 1100 (see FIG. 41) that may snap ontoa portion of the set or fluid line.

FIG. 216 shows a flowchart outlining steps which may be used to programand collected an automated effluent sample using a cycler. As shown, instep 5720, the user begins programming a therapy. This may involvespecifying various therapy parameters such as any of those commonlydefined in the art on a user interface of the cycler. In step 5722 auser enables an automated sampling option or parameter. This may be doneusing a user interface of the cycler. In some embodiments, the user maythen choose between a customized or user specified sampling program or apreset sampling program. This may in some embodiments be accomplished byuser interaction with a prompt displayed on the user interface of thecycler.

If a user chooses to use a preset sampling program or regimen, thecycler displays a list of one or more preset regimens on the userinterface of the device in step 5724. These preset regimens may forexample include a peritonitis test, peritoneal equalization test, singlesample, etc. In some embodiments, these presets may be tied to otherparameters programmed during the therapy. For example, when a preset isselected the amount of fluid to be pumped into the sampling reservoirmay be dependent upon the patient fill volume. Additionally, in someinstances a user may have to enter one or more additional parameter oncea preset has been selected. For example, if a user selects that a singlesample is to be collected, the user may be required to define when inthe therapy this is to occur. A user may select the desired samplingregimen or program from the list in step 5726. This may be done via anysuitable type of interaction with the user interface of the cycler. Theuser may then finish programming the therapy in step 5728.

If a user chooses to define a user specified or custom sampling regimen,the cycler may display one or more parameters related to the automatedsampling on the user interface of the cycler in step 5730. The user maythen define one or more parameter related to the automated sampling tobe performed by the cycler in step 5732. This may be done via anysuitable type of interaction with the user interface of the cycler. Theparameters defined may be, but are not limited to any of those mentionedabove. The user may then finish programming the therapy in step 5734.

The therapy is started in step 5736. The therapy continues as programmedin step 5738 until it is time for an automated sample to be taken by thecycler. Once it is time for the sample to be taken, the cycler takes thesample as specified by the therapy program in step 5740. If there areadditional samples to be taken during the therapy, the cycler proceedsback to step 5738 and continues the therapy until it is time to takeanother sample. If there are no additional samples to be taken in thetherapy, the cycler completes the therapy in step 5742.

FIG. 217 depicts a flowchart detailing a number of example steps whichmay be used to program and collected an automated effluent sample usinga cycler. In the example embodiment, the cycler includes a sensor whichis configured to read an indicia on a set. The indicia on the set mayinclude information about the set or the therapy to be performed. Theindicia may also specify whether or not and the manner in which anautomated effluent sample is to be taken by the cycler.

As shown, in step 5750, the user installs the set in the cycler. Thecycler may then read the indicia on the set 5752. The therapy is startedin step 5754. In the event that the indicia indicates that an automatedsample is not to be taken during the therapy, the cycler performs andcompletes the therapy in step 5760.

If the indicia specifies an automated sampling regimen or program, thetherapy continues as programmed in step 5756 until it is time for anautomated sample to be taken by the cycler. Once it is time for thesample to be taken, the cycler takes the sample as specified by indiciain step 5758. In alternate embodiments, the indicia may specify whetherthe sample is to be taken and the cycler performs a preprogrammedsampling procedure. If there are additional samples to be taken duringthe therapy, the cycler proceeds back to step 5756 and continues thetherapy until it is time to take another sample. If there are noadditional samples to be taken in the therapy, the cycler completes thetherapy in step 5760.

While aspects of the invention have been described in conjunction withspecific embodiments thereof, it is evident that many alternatives,modifications, and variations will be apparent to those skilled in theart. Accordingly, embodiments of the invention as set forth herein areintended to be illustrative, not limiting. Various changes may be madewithout departing from the spirit and scope of the invention.

The invention claimed is:
 1. A system for measuring a volume of apneumatically actuated control chamber of a pneumatically actuateddiaphragm pump, comprising: a fluid inlet valve and a fluid outlet valveconnected to a pumping chamber of the pneumatically actuated diaphragmpump; a diaphragm separating the control chamber from the pumpingchamber, the control chamber fluidly connected to a reference chamber ofa known volume via a conduit that includes a reference chamber valve;the control chamber fluidly connected via one or more actuation valvesto a source of positive or negative pneumatic pressure; a controllerconfigured to control the fluid inlet valve and the fluid outlet valve,the reference chamber valve, and the one or more actuation valves, andto receive pressure data from a first pressure sensor connected to thecontrol chamber and a second pressure sensor connected to the referencechamber; wherein the controller is configured to isolate the pumpingchamber by closing the fluid inlet valve and the fluid outlet valve,charge the control chamber with a first control chamber pressure; ventthe reference chamber or fix a pneumatic pressure in the referencechamber that is different from the first control chamber pressure:measure the first control chamber pressure and a second referencechamber pressure, connect the control chamber to the reference chamberby opening the reference chamber valve and equalizing pressures betweenthe control chamber and the reference chamber, and measure a thirdequalized pressure in the control chamber and the reference chamber, andwherein the controller is configured to compute the volume of thecontrol chamber based on an ideal gas model that assumes an adiabaticpressure equalization process in the reference chamber and a polytropicpressure equalization process in the control chamber, wherein the idealgas model applied to the control chamber uses a polytropic coefficientand the controller is programed to adjust a value of the polytropiccoefficient as a pre-defined function of the volume of the controlchamber.
 2. The system of claim 1, wherein the ideal gas model furtherassumes an isothermal process in the conduit as a gas moves from thecontrol chamber to the reference chamber during the equalizing pressuresbetween the control chamber and the reference chamber.
 3. The system ofclaim 1, wherein the controller is programmed to compute the polytropiccoefficient based on an estimated volume of the control chamber using amodel that assumes an adiabatic pressure equalization process in thecontrol chamber.
 4. A system for measuring a volume of a pneumaticallyactuated control chamber of a pneumatically actuated diaphragm pump,comprising: a fluid inlet valve and a fluid outlet valve connected to apumping chamber of the pneumatically actuated diaphragm pump; adiaphragm separating the control chamber from the pumping chamber, thecontrol chamber fluidly connected to a reference chamber of a knownvolume via a conduit that includes a reference chamber valve; thecontrol chamber fluidly connected via one or more actuation valves to asource of positive or negative pneumatic pressure: a controllerconfigured to control the fluid inlet valve and the fluid outlet valve,the reference chamber valve, and the one or more actuation valves, andto receive pressure data from a first pressure sensor connected to thecontrol chamber and a second pressure sensor connected to the referencechamber: wherein the controller is configured to isolate the pumpingchamber by closing the fluid inlet valve and the fluid outlet valve,charge the control chamber with a first control chamber pressure; ventthe reference chamber or fix a pneumatic pressure in the referencechamber that is different from the first control chamber pressure:measure the first control chamber pressure and a second referencechamber pressure, connect the control chamber to the reference chamberby opening the reference chamber valve and equalizing pressures betweenthe control chamber and the reference chamber, and measure a thirdequalized pressure in the control chamber and the reference chamber, andwherein the controller is configured to compute the volume of thecontrol chamber based on an ideal gas model under a polytropic process,wherein the controller is configured to select a polytropic coefficientfor the ideal gas model using a pre-determined function in which a valueof the polytropic coefficient depends on and varies with the volume ofthe control chamber.
 5. The system of claim 4, wherein thepre-determined function is determined by fixing the volume of thecontrol chamber at a known volume, and calculating the polytropiccoefficient corresponding to the known volumes of the control chamberand the reference chamber, and the measured first control chamberpressure, the measured second reference chamber pressure, and themeasured third equalized pressure; wherein said calculation is repeateda plurality of times, each time of the plurality of times correspondingto fixing the volume of the control chamber at a different known volume.6. The system of claim 5, wherein the pre-determined functioncorresponds to a stored look-up table from which the controller selectsthe polytropic coefficient corresponding to the volume of the controlchamber being computed.
 7. The system of claim 5, wherein thepre-determined function corresponds to an equation that has been fittedto a plurality of calculated polytropic coefficients corresponding to aseries of known control chamber volumes.